From b07882e3f41bc5138bbc5db210f21f45bc67aeea Mon Sep 17 00:00:00 2001
From: Thanakorn S <ts_nok@hotmail.com>
Date: Sat, 23 May 2026 17:06:08 +0700
Subject: [PATCH] code audit fixes: require_once, issue flow, role guards

- Upgraded all plain `require` to `require_once` across 172 api/engine
  and api/engine_report files to prevent class-redeclaration errors
- Added issue button, issue_invoice() with GL toastr, and delete_invoice()
  to expense/manage_purchase_invoice.php, bringing it in line with
  po/manage_purchase_invoice.php
- Added can_delete role guard (admin/owner only) to trash icons on
  revenue/invoice.php and expense/purchase_invoice.php, matching the
  existing pattern in finance/receipt.php and finance/payment.php

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 app/ac_dashboard/api/engine/by_source.php     |  6 +-
 app/ac_dashboard/api/engine/journals.php      |  6 +-
 app/ac_dashboard/api/engine/pl.php            |  6 +-
 .../api/engine/posting_window.php             |  2 +-
 app/ac_dashboard/api/engine/recent.php        |  6 +-
 app/ac_dashboard/api/engine/trend.php         |  6 +-
 app/accounting/api/engine/account.php         |  4 +-
 app/accounting/api/engine/account_formula.php |  4 +-
 app/accounting/api/engine/account_stats.php   |  4 +-
 app/accounting/api/engine/acquire_op_lock.php |  4 +-
 app/accounting/api/engine/department.php      |  4 +-
 .../api/engine/department_stats.php           |  4 +-
 .../api/engine/get_balance_sheet.php          |  6 +-
 .../api/engine/get_gl_by_source.php           |  2 +-
 .../api/engine/get_gl_documents.php           |  4 +-
 app/accounting/api/engine/get_gl_movement.php |  6 +-
 .../api/engine/get_journal_detail.php         |  4 +-
 .../api/engine/get_journal_listing.php        |  4 +-
 .../api/engine/get_pl_statement.php           |  6 +-
 .../api/engine/get_trial_balance.php          |  6 +-
 app/accounting/api/engine/get_vat_report.php  |  6 +-
 .../api/engine/log_batch_action.php           |  4 +-
 app/accounting/api/engine/manage_account.php  |  4 +-
 .../api/engine/manage_department.php          |  4 +-
 app/accounting/api/engine/post_gl_entry.php   | 22 ++---
 app/accounting/api/engine/posting_window.php  |  2 +-
 .../api/engine/product_account_mapping.php    |  6 +-
 app/accounting/api/engine/release_op_lock.php |  4 +-
 app/accounting/api/engine/remove_account.php  |  4 +-
 .../api/engine/remove_department.php          |  4 +-
 .../api/engine/retrieve_account.php           |  4 +-
 .../api/engine/retrieve_department.php        |  4 +-
 .../api/engine/save_manual_journal.php        |  6 +-
 app/contact/api/engine/contact.php            |  4 +-
 app/contact/api/engine/contact_stats.php      |  4 +-
 app/contact/api/engine/contact_type.php       |  4 +-
 app/contact/api/engine/manage_contact.php     |  6 +-
 .../api/engine/manage_contact_type.php        |  4 +-
 app/contact/api/engine/remove_contact.php     |  4 +-
 .../api/engine/remove_contact_type.php        |  4 +-
 app/contact/api/engine/retrieve_contact.php   |  4 +-
 .../api/engine/retrieve_contact_type.php      |  4 +-
 app/dashboard/api/engine_report/low_stock.php |  4 +-
 .../api/engine_report/reports_stats.php       |  6 +-
 .../api/engine/convert_purchase_request.php   |  6 +-
 .../api/engine/manage_purchase_request.php    |  4 +-
 .../engine/manage_supplier_credit_note.php    |  4 +-
 .../api/engine/retrieve_purchase_request.php  |  4 +-
 .../engine/update_purchase_request_status.php |  4 +-
 app/expense/manage_purchase_invoice.php       | 80 ++++++++++++++++++-
 app/expense/purchase_invoice.php              |  9 +--
 app/finance/api/engine/delete_payment.php     |  4 +-
 .../api/engine/delete_payment_billing.php     |  4 +-
 app/finance/api/engine/delete_receipt.php     |  4 +-
 .../api/engine/delete_receipt_billing.php     |  4 +-
 app/finance/api/engine/manage_payment.php     |  6 +-
 .../api/engine/manage_payment_billing.php     |  4 +-
 app/finance/api/engine/manage_receipt.php     |  6 +-
 .../api/engine/manage_receipt_billing.php     |  4 +-
 app/ics/api/engine/approve_stock.php          |  6 +-
 app/ics/api/engine/barcode_lookup.php         |  4 +-
 app/ics/api/engine/contact_search.php         |  4 +-
 app/ics/api/engine/delete_stock_in.php        |  4 +-
 app/ics/api/engine/delete_stock_out.php       |  4 +-
 app/ics/api/engine/delete_stock_transfer.php  |  4 +-
 app/ics/api/engine/location_barcode_label.php |  4 +-
 app/ics/api/engine/manage_stock_in.php        |  8 +-
 app/ics/api/engine/manage_stock_out.php       |  8 +-
 app/ics/api/engine/manage_stock_transfer.php  |  8 +-
 app/ics/api/engine/product_search.php         |  4 +-
 app/ics/api/engine/retrieve_active_lot.php    |  4 +-
 app/ics/api/engine/retrieve_active_serial.php |  4 +-
 app/ics/api/engine/retrieve_aisle.php         |  4 +-
 app/ics/api/engine/retrieve_lot.php           |  4 +-
 app/ics/api/engine/retrieve_rack.php          |  4 +-
 .../api/engine/retrieve_stock_by_source.php   |  4 +-
 app/ics/api/engine/retrieve_stock_in.php      |  4 +-
 app/ics/api/engine/retrieve_stock_out.php     |  4 +-
 .../api/engine/retrieve_stock_transfer.php    |  4 +-
 app/ics/api/engine/retrieve_warehouse.php     |  4 +-
 app/ics/api/engine/retrieve_zone.php          |  4 +-
 app/ics/api/engine/sku_barcode_label.php      |  4 +-
 app/ics/api/engine/sku_label_lots.php         |  4 +-
 app/ics/api/engine/sku_label_products.php     |  4 +-
 app/ics/api/engine/stock_in.php               |  4 +-
 app/ics/api/engine/stock_out.php              |  4 +-
 app/ics/api/engine/stock_transfer.php         |  4 +-
 app/ics/api/engine/validate_scan_location.php |  4 +-
 app/ics/api/engine_report/product_stats.php   |  4 +-
 app/ics/api/engine_report/stock_activity.php  |  4 +-
 app/ics/api/engine_report/stock_movement.php  |  4 +-
 app/ics/api/engine_report/stock_trend.php     |  4 +-
 .../api/engine_report/warehouse_balance.php   |  4 +-
 .../api/engine_report/warehouse_overview.php  |  4 +-
 app/ics/api/engine_report/warehouse_stats.php |  4 +-
 app/inventory/api/engine/manage_category.php  |  4 +-
 app/inventory/api/engine/manage_product.php   |  6 +-
 app/inventory/api/engine/manage_storage.php   |  4 +-
 app/inventory/api/engine/manage_warehouse.php |  4 +-
 app/inventory/api/engine/manager.php          |  4 +-
 app/inventory/api/engine/product.php          |  4 +-
 app/inventory/api/engine/product_category.php |  4 +-
 app/inventory/api/engine/product_stats.php    |  4 +-
 app/inventory/api/engine/remove_category.php  |  4 +-
 app/inventory/api/engine/remove_product.php   |  4 +-
 app/inventory/api/engine/remove_storage.php   |  4 +-
 app/inventory/api/engine/remove_warehouse.php |  4 +-
 .../api/engine/retrieve_category.php          |  4 +-
 app/inventory/api/engine/retrieve_product.php |  4 +-
 app/inventory/api/engine/retrieve_storage.php |  4 +-
 .../api/engine/retrieve_warehouse.php         |  4 +-
 app/inventory/api/engine/storage.php          |  4 +-
 app/inventory/api/engine/warehouse.php        |  4 +-
 app/inventory/api/engine/warehouse_stats.php  |  4 +-
 app/login/api/engine/back.php                 |  4 +-
 app/login/api/engine/invited_onboarding.php   | 10 +--
 app/login/api/engine/login_confirm.php        |  8 +-
 app/login/api/engine/login_otp.php            |  8 +-
 app/login/api/engine/onboarding.php           |  8 +-
 app/login/api/engine/register.php             | 10 +--
 app/login/api/engine/request_new_otp.php      |  8 +-
 app/login/api/engine/request_reset_otp.php    |  4 +-
 app/login/api/engine/reset_password_otp.php   |  4 +-
 app/order/api/engine/cancel_order.php         |  6 +-
 app/order/api/engine/cancel_return.php        |  6 +-
 app/order/api/engine/confirm_order.php        | 10 +--
 app/order/api/engine/confirm_return.php       |  8 +-
 app/order/api/engine/delete_invoice.php       |  4 +-
 app/order/api/engine/delete_order.php         |  6 +-
 app/order/api/engine/delete_return.php        |  6 +-
 app/order/api/engine/issue_invoice.php        |  4 +-
 app/order/api/engine/manage_invoice.php       |  6 +-
 app/order/api/engine/manage_order.php         |  6 +-
 app/order/api/engine/manage_return.php        |  4 +-
 .../api/engine/proceed_to_credit_note.php     |  4 +-
 app/order/api/engine/proceed_to_invoice.php   |  4 +-
 app/order/api/engine/retrieve_invoice.php     |  4 +-
 app/order/api/engine/retrieve_order.php       |  4 +-
 app/order/api/engine/retrieve_return.php      |  4 +-
 .../api/engine/update_invoice_status.php      |  4 +-
 app/order/api/engine/update_order_status.php  |  4 +-
 app/order/api/engine/void_invoice.php         |  4 +-
 app/po/api/engine/cancel_po.php               |  4 +-
 app/po/api/engine/cancel_supplier_return.php  |  6 +-
 app/po/api/engine/close_po.php                |  4 +-
 app/po/api/engine/confirm_po.php              |  4 +-
 app/po/api/engine/confirm_supplier_return.php |  8 +-
 app/po/api/engine/delete_po.php               |  6 +-
 app/po/api/engine/delete_purchase_request.php |  4 +-
 app/po/api/engine/delete_supplier_return.php  |  6 +-
 app/po/api/engine/manage_po.php               |  6 +-
 app/po/api/engine/manage_supplier_return.php  |  4 +-
 .../engine/proceed_to_purchase_invoice.php    |  4 +-
 .../proceed_to_supplier_credit_note.php       |  4 +-
 app/po/api/engine/receive_po.php              |  8 +-
 app/po/api/engine/retrieve_po.php             |  4 +-
 .../api/engine/retrieve_supplier_return.php   |  4 +-
 app/po/api/engine/update_po_payment.php       |  4 +-
 .../api/engine_report/expired_stock.php       |  6 +-
 .../api/engine_report/lot_stock_log.php       |  6 +-
 app/reports/api/engine_report/product_lot.php |  6 +-
 app/reports/api/engine_report/rack_log.php    |  6 +-
 .../api/engine_report/rack_occupancy.php      |  6 +-
 .../api/engine_report/stock_movement.php      |  6 +-
 .../api/engine_report/stock_movement_sku.php  |  6 +-
 app/revenue/api/engine/convert_quotation.php  |  6 +-
 app/revenue/api/engine/delete_quotation.php   |  4 +-
 app/revenue/api/engine/manage_credit_note.php |  4 +-
 app/revenue/api/engine/manage_order.php       |  6 +-
 app/revenue/api/engine/manage_quotation.php   |  6 +-
 app/revenue/api/engine/proceed_to_invoice.php |  6 +-
 app/revenue/api/engine/quotation_stats.php    |  4 +-
 app/revenue/api/engine/retrieve_quotation.php |  4 +-
 .../api/engine/update_quotation_status.php    |  4 +-
 app/revenue/invoice.php                       |  9 +--
 app/setting/api/engine/change_password.php    |  4 +-
 app/setting/api/engine/company_setting.php    |  2 +-
 app/setting/api/engine/gl_maintenance.php     |  2 +-
 app/setting/api/engine/manage_company.php     |  4 +-
 app/setting/api/engine/manage_profile.php     |  6 +-
 app/setting/api/engine/manage_smtp.php        |  4 +-
 app/setting/api/engine/manage_users.php       |  4 +-
 app/setting/api/engine/request_reset_otp.php  |  4 +-
 app/setting/api/engine/reset_password_otp.php |  4 +-
 app/setting/api/engine/retrieve_company.php   |  4 +-
 app/setting/api/engine/retrieve_profile.php   |  4 +-
 app/setting/api/engine/retrieve_smtp.php      |  4 +-
 app/setting/api/engine/retrieve_users.php     |  4 +-
 app/setting/api/engine/search_users.php       |  4 +-
 app/setting/api/engine/switch_branch.php      |  4 +-
 app/setting/api/engine/test_smtp.php          |  4 +-
 191 files changed, 534 insertions(+), 464 deletions(-)

diff --git a/app/ac_dashboard/api/engine/by_source.php b/app/ac_dashboard/api/engine/by_source.php
index 0de7653..b721ba3 100644
--- a/app/ac_dashboard/api/engine/by_source.php
+++ b/app/ac_dashboard/api/engine/by_source.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
-    require '../../../assets/utils/classes_ac/FinancialReports.php';
+    require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
     $reports = new FinancialReports($pdo2, $company_id);
 
diff --git a/app/ac_dashboard/api/engine/journals.php b/app/ac_dashboard/api/engine/journals.php
index 144a4d7..74d2b8b 100644
--- a/app/ac_dashboard/api/engine/journals.php
+++ b/app/ac_dashboard/api/engine/journals.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
-    require '../../../assets/utils/classes_ac/FinancialReports.php';
+    require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
     $reports = new FinancialReports($pdo2, $company_id);
 
diff --git a/app/ac_dashboard/api/engine/pl.php b/app/ac_dashboard/api/engine/pl.php
index 7d631c7..eedfb66 100644
--- a/app/ac_dashboard/api/engine/pl.php
+++ b/app/ac_dashboard/api/engine/pl.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
-    require '../../../assets/utils/classes_ac/FinancialReports.php';
+    require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
     $reports = new FinancialReports($pdo2, $company_id);
 
diff --git a/app/ac_dashboard/api/engine/posting_window.php b/app/ac_dashboard/api/engine/posting_window.php
index 664b768..4f1b05c 100644
--- a/app/ac_dashboard/api/engine/posting_window.php
+++ b/app/ac_dashboard/api/engine/posting_window.php
@@ -1,6 +1,6 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $settings  = new CompanySettingManager($pdo1, $company_id);
diff --git a/app/ac_dashboard/api/engine/recent.php b/app/ac_dashboard/api/engine/recent.php
index 4b61848..f0014f5 100644
--- a/app/ac_dashboard/api/engine/recent.php
+++ b/app/ac_dashboard/api/engine/recent.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
-    require '../../../assets/utils/classes_ac/FinancialReports.php';
+    require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
     $limit   = max(1, min(50, (int)($data['limit'] ?? 10)));
     $reports = new FinancialReports($pdo2, $company_id);
diff --git a/app/ac_dashboard/api/engine/trend.php b/app/ac_dashboard/api/engine/trend.php
index 8a063b8..cc08acb 100644
--- a/app/ac_dashboard/api/engine/trend.php
+++ b/app/ac_dashboard/api/engine/trend.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
-    require '../../../assets/utils/classes_ac/FinancialReports.php';
+    require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
     $months  = max(1, min(24, (int)($data['months'] ?? 6)));
     $reports = new FinancialReports($pdo2, $company_id);
diff --git a/app/accounting/api/engine/account.php b/app/accounting/api/engine/account.php
index 1a3bed4..dc93c73 100644
--- a/app/accounting/api/engine/account.php
+++ b/app/accounting/api/engine/account.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 $coa = new ChartOfAccounts($pdo2, $company_id);
 $answer['output']  = $coa->getAll();
diff --git a/app/accounting/api/engine/account_formula.php b/app/accounting/api/engine/account_formula.php
index bb25a9f..e593300 100644
--- a/app/accounting/api/engine/account_formula.php
+++ b/app/accounting/api/engine/account_formula.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin', 'staff']);
-require '../../../assets/utils/classes_ac/AccountFormulaManager.php';
+require_once '../../../assets/utils/classes_ac/AccountFormulaManager.php';
 
 try {
     $mgr = new AccountFormulaManager($pdo2, $company_id);
diff --git a/app/accounting/api/engine/account_stats.php b/app/accounting/api/engine/account_stats.php
index 5811abc..6be7eb3 100644
--- a/app/accounting/api/engine/account_stats.php
+++ b/app/accounting/api/engine/account_stats.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 $coa = new ChartOfAccounts($pdo2, $company_id);
 $stats = $coa->getStats();
diff --git a/app/accounting/api/engine/acquire_op_lock.php b/app/accounting/api/engine/acquire_op_lock.php
index ee0a1f3..9d756ff 100644
--- a/app/accounting/api/engine/acquire_op_lock.php
+++ b/app/accounting/api/engine/acquire_op_lock.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/OperationLockManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/OperationLockManager.php';
 
 try {
     $lock_manager = new OperationLockManager($pdo2, $company_id, $user_id);
diff --git a/app/accounting/api/engine/department.php b/app/accounting/api/engine/department.php
index 5d7021e..9389191 100644
--- a/app/accounting/api/engine/department.php
+++ b/app/accounting/api/engine/department.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/DepartmentManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/DepartmentManager.php';
 
 $dept = new DepartmentManager($pdo2, $company_id);
 $answer['output']  = $dept->getAll();
diff --git a/app/accounting/api/engine/department_stats.php b/app/accounting/api/engine/department_stats.php
index 69d0148..d2b421a 100644
--- a/app/accounting/api/engine/department_stats.php
+++ b/app/accounting/api/engine/department_stats.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/DepartmentManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/DepartmentManager.php';
 
 $dept   = new DepartmentManager($pdo2, $company_id);
 $stats  = $dept->getStats();
diff --git a/app/accounting/api/engine/get_balance_sheet.php b/app/accounting/api/engine/get_balance_sheet.php
index a2dfa83..20fea7c 100644
--- a/app/accounting/api/engine/get_balance_sheet.php
+++ b/app/accounting/api/engine/get_balance_sheet.php
@@ -1,10 +1,10 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-require '../../../assets/utils/classes_ac/FinancialReports.php';
+require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
 $as_of_date = trim((string)($data['as_of_date'] ?? ($data['as_of_period'] ?? date('Y-m-d'))));
 $dept_id    = (int)($data['department_id'] ?? 0);
diff --git a/app/accounting/api/engine/get_gl_by_source.php b/app/accounting/api/engine/get_gl_by_source.php
index b116304..6a07ee5 100644
--- a/app/accounting/api/engine/get_gl_by_source.php
+++ b/app/accounting/api/engine/get_gl_by_source.php
@@ -1,6 +1,6 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_once '../../../assets/utils/classes_ac/GlManager.php';
 require_once '../../../assets/utils/classes_ac/GlQueryManager.php';
 
diff --git a/app/accounting/api/engine/get_gl_documents.php b/app/accounting/api/engine/get_gl_documents.php
index 027fa3b..8cd291b 100644
--- a/app/accounting/api/engine/get_gl_documents.php
+++ b/app/accounting/api/engine/get_gl_documents.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/GlQueryManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/GlQueryManager.php';
 
 try {
     $gl_query = new GlQueryManager($pdo2, $company_id);
diff --git a/app/accounting/api/engine/get_gl_movement.php b/app/accounting/api/engine/get_gl_movement.php
index 956d0f2..8263bdc 100644
--- a/app/accounting/api/engine/get_gl_movement.php
+++ b/app/accounting/api/engine/get_gl_movement.php
@@ -1,10 +1,10 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-require '../../../assets/utils/classes_ac/FinancialReports.php';
+require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
 $account_code = trim((string)($data['account_code'] ?? ''));
 $from_date    = trim((string)($data['from_date']    ?? ($data['from_period'] ?? date('Y-m-d'))));
diff --git a/app/accounting/api/engine/get_journal_detail.php b/app/accounting/api/engine/get_journal_detail.php
index 90fb3b6..e2e310c 100644
--- a/app/accounting/api/engine/get_journal_detail.php
+++ b/app/accounting/api/engine/get_journal_detail.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/GlQueryManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/GlQueryManager.php';
 
 try {
     $gl_query = new GlQueryManager($pdo2, $company_id);
diff --git a/app/accounting/api/engine/get_journal_listing.php b/app/accounting/api/engine/get_journal_listing.php
index 31860cd..7a5e5f6 100644
--- a/app/accounting/api/engine/get_journal_listing.php
+++ b/app/accounting/api/engine/get_journal_listing.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/GlQueryManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/GlQueryManager.php';
 
 try {
     $gl_query = new GlQueryManager($pdo2, $company_id);
diff --git a/app/accounting/api/engine/get_pl_statement.php b/app/accounting/api/engine/get_pl_statement.php
index 4a7fe32..04796ad 100644
--- a/app/accounting/api/engine/get_pl_statement.php
+++ b/app/accounting/api/engine/get_pl_statement.php
@@ -1,10 +1,10 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-require '../../../assets/utils/classes_ac/FinancialReports.php';
+require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
 $from_date = trim((string)($data['from_date'] ?? ($data['from_period'] ?? date('Y-m-d'))));
 $to_date   = trim((string)($data['to_date']   ?? ($data['to_period']   ?? $from_date)));
diff --git a/app/accounting/api/engine/get_trial_balance.php b/app/accounting/api/engine/get_trial_balance.php
index 4a18c8d..e2e029f 100644
--- a/app/accounting/api/engine/get_trial_balance.php
+++ b/app/accounting/api/engine/get_trial_balance.php
@@ -1,10 +1,10 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-require '../../../assets/utils/classes_ac/FinancialReports.php';
+require_once '../../../assets/utils/classes_ac/FinancialReports.php';
 
 $from_date = trim((string)($data['from_date'] ?? ($data['from_period'] ?? date('Y-m-d'))));
 $to_date   = trim((string)($data['to_date']   ?? ($data['to_period']   ?? $from_date)));
diff --git a/app/accounting/api/engine/get_vat_report.php b/app/accounting/api/engine/get_vat_report.php
index cc0250b..49c3612 100644
--- a/app/accounting/api/engine/get_vat_report.php
+++ b/app/accounting/api/engine/get_vat_report.php
@@ -1,10 +1,10 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-require '../../../assets/utils/classes_ac/TaxReportManager.php';
+require_once '../../../assets/utils/classes_ac/TaxReportManager.php';
 
 $from_date  = trim((string)($data['from_date'] ?? ($data['from_period'] ?? date('Y-m-d'))));
 $to_date    = trim((string)($data['to_date']   ?? ($data['to_period']   ?? $from_date)));
diff --git a/app/accounting/api/engine/log_batch_action.php b/app/accounting/api/engine/log_batch_action.php
index 5dcd4bb..da121ba 100644
--- a/app/accounting/api/engine/log_batch_action.php
+++ b/app/accounting/api/engine/log_batch_action.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/BatchActionManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/BatchActionManager.php';
 
 try {
     $batch_action = new BatchActionManager($pdo2, $company_id, $user_id);
diff --git a/app/accounting/api/engine/manage_account.php b/app/accounting/api/engine/manage_account.php
index 57703ab..e6f15d4 100644
--- a/app/accounting/api/engine/manage_account.php
+++ b/app/accounting/api/engine/manage_account.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/manage_department.php b/app/accounting/api/engine/manage_department.php
index 85b9d6a..9a02d73 100644
--- a/app/accounting/api/engine/manage_department.php
+++ b/app/accounting/api/engine/manage_department.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/DepartmentManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/DepartmentManager.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/post_gl_entry.php b/app/accounting/api/engine/post_gl_entry.php
index 068baad..aad8114 100644
--- a/app/accounting/api/engine/post_gl_entry.php
+++ b/app/accounting/api/engine/post_gl_entry.php
@@ -1,16 +1,16 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/PostingWindowGuard.php';
-require '../../../assets/utils/classes_ac/GlManager.php';
-require '../../../assets/utils/classes_ac/posting/BasePosting.php';
-require '../../../assets/utils/classes_ac/posting/InvoicePosting.php';
-require '../../../assets/utils/classes_ac/posting/CreditNotePosting.php';
-require '../../../assets/utils/classes_ac/posting/PurchaseInvoicePosting.php';
-require '../../../assets/utils/classes_ac/posting/SupplierCreditNotePosting.php';
-require '../../../assets/utils/classes_ac/posting/ReceiptPosting.php';
-require '../../../assets/utils/classes_ac/posting/PaymentPosting.php';
-require '../../../assets/utils/classes_ac/posting/PurchasePosting.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/PostingWindowGuard.php';
+require_once '../../../assets/utils/classes_ac/GlManager.php';
+require_once '../../../assets/utils/classes_ac/posting/BasePosting.php';
+require_once '../../../assets/utils/classes_ac/posting/InvoicePosting.php';
+require_once '../../../assets/utils/classes_ac/posting/CreditNotePosting.php';
+require_once '../../../assets/utils/classes_ac/posting/PurchaseInvoicePosting.php';
+require_once '../../../assets/utils/classes_ac/posting/SupplierCreditNotePosting.php';
+require_once '../../../assets/utils/classes_ac/posting/ReceiptPosting.php';
+require_once '../../../assets/utils/classes_ac/posting/PaymentPosting.php';
+require_once '../../../assets/utils/classes_ac/posting/PurchasePosting.php';
 
 require_role($user_role, ['owner', 'admin']);
 require_once '../../../assets/utils/notify_node.php';
diff --git a/app/accounting/api/engine/posting_window.php b/app/accounting/api/engine/posting_window.php
index 899e340..ac5a550 100644
--- a/app/accounting/api/engine/posting_window.php
+++ b/app/accounting/api/engine/posting_window.php
@@ -1,6 +1,6 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_once '../../../assets/utils/classes/CompanySettingManager.php';
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/product_account_mapping.php b/app/accounting/api/engine/product_account_mapping.php
index c6e6511..2f00e07 100644
--- a/app/accounting/api/engine/product_account_mapping.php
+++ b/app/accounting/api/engine/product_account_mapping.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/ProductManager.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/ProductManager.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/release_op_lock.php b/app/accounting/api/engine/release_op_lock.php
index 96246db..f4d11ec 100644
--- a/app/accounting/api/engine/release_op_lock.php
+++ b/app/accounting/api/engine/release_op_lock.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/OperationLockManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/OperationLockManager.php';
 
 try {
     $lock_manager = new OperationLockManager($pdo2, $company_id, $user_id);
diff --git a/app/accounting/api/engine/remove_account.php b/app/accounting/api/engine/remove_account.php
index ca90ef6..fd661bd 100644
--- a/app/accounting/api/engine/remove_account.php
+++ b/app/accounting/api/engine/remove_account.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/remove_department.php b/app/accounting/api/engine/remove_department.php
index e3bcc7b..12d8f75 100644
--- a/app/accounting/api/engine/remove_department.php
+++ b/app/accounting/api/engine/remove_department.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/DepartmentManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/DepartmentManager.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/accounting/api/engine/retrieve_account.php b/app/accounting/api/engine/retrieve_account.php
index 25797e1..d583846 100644
--- a/app/accounting/api/engine/retrieve_account.php
+++ b/app/accounting/api/engine/retrieve_account.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/ChartOfAccounts.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/ChartOfAccounts.php';
 
 $id = (int)($data['id'] ?? 0);
 if (!$id) {
diff --git a/app/accounting/api/engine/retrieve_department.php b/app/accounting/api/engine/retrieve_department.php
index eaa47cf..3c2638e 100644
--- a/app/accounting/api/engine/retrieve_department.php
+++ b/app/accounting/api/engine/retrieve_department.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/DepartmentManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/DepartmentManager.php';
 
 $id = (int)($data['id'] ?? 0);
 if (!$id) { $answer['message'] = 'Missing id'; exit(json_encode($answer)); }
diff --git a/app/accounting/api/engine/save_manual_journal.php b/app/accounting/api/engine/save_manual_journal.php
index fd31fea..0f7497e 100644
--- a/app/accounting/api/engine/save_manual_journal.php
+++ b/app/accounting/api/engine/save_manual_journal.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes_ac/PostingWindowGuard.php';
-require '../../../assets/utils/classes_ac/GlManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes_ac/PostingWindowGuard.php';
+require_once '../../../assets/utils/classes_ac/GlManager.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/contact/api/engine/contact.php b/app/contact/api/engine/contact.php
index fa173e6..7caa1a2 100644
--- a/app/contact/api/engine/contact.php
+++ b/app/contact/api/engine/contact.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     $contact = new ContactManager($pdo2, $company_id);
     $answer['output']  = $contact->getContactList();
diff --git a/app/contact/api/engine/contact_stats.php b/app/contact/api/engine/contact_stats.php
index 2149893..a08477e 100644
--- a/app/contact/api/engine/contact_stats.php
+++ b/app/contact/api/engine/contact_stats.php
@@ -1,8 +1,8 @@
 <?php 
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/contact/api/engine/contact_type.php b/app/contact/api/engine/contact_type.php
index 752c150..0a6849e 100644
--- a/app/contact/api/engine/contact_type.php
+++ b/app/contact/api/engine/contact_type.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     $contact = new ContactManager($pdo2, $company_id);
     $answer['output']  = $contact->getContactTypeList();
diff --git a/app/contact/api/engine/manage_contact.php b/app/contact/api/engine/manage_contact.php
index bd5573f..dfd55a9 100644
--- a/app/contact/api/engine/manage_contact.php
+++ b/app/contact/api/engine/manage_contact.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/FileUploader.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/FileUploader.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     require_role($user_role, ['owner', 'admin', 'staff']);
 
diff --git a/app/contact/api/engine/manage_contact_type.php b/app/contact/api/engine/manage_contact_type.php
index f24ac5c..a0c056c 100644
--- a/app/contact/api/engine/manage_contact_type.php
+++ b/app/contact/api/engine/manage_contact_type.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/contact/api/engine/remove_contact.php b/app/contact/api/engine/remove_contact.php
index 7f82c3a..21e1269 100644
--- a/app/contact/api/engine/remove_contact.php
+++ b/app/contact/api/engine/remove_contact.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/contact/api/engine/remove_contact_type.php b/app/contact/api/engine/remove_contact_type.php
index 593120d..67e774b 100644
--- a/app/contact/api/engine/remove_contact_type.php
+++ b/app/contact/api/engine/remove_contact_type.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/contact/api/engine/retrieve_contact.php b/app/contact/api/engine/retrieve_contact.php
index 1887828..3ee2647 100644
--- a/app/contact/api/engine/retrieve_contact.php
+++ b/app/contact/api/engine/retrieve_contact.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     $contact = new ContactManager($pdo2, $company_id);
     $answer['contact_dir'] = $include_url . 'uploads/contact/';
diff --git a/app/contact/api/engine/retrieve_contact_type.php b/app/contact/api/engine/retrieve_contact_type.php
index a6d12c2..e514aa6 100644
--- a/app/contact/api/engine/retrieve_contact_type.php
+++ b/app/contact/api/engine/retrieve_contact_type.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     $contact = new ContactManager($pdo2, $company_id);
     $answer['output']  = $contact->getContactTypeById((int)$data['id']);
diff --git a/app/dashboard/api/engine_report/low_stock.php b/app/dashboard/api/engine_report/low_stock.php
index 06df6b9..2026e19 100644
--- a/app/dashboard/api/engine_report/low_stock.php
+++ b/app/dashboard/api/engine_report/low_stock.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/dashboard/api/engine_report/reports_stats.php b/app/dashboard/api/engine_report/reports_stats.php
index d7a7b55..70cc027 100644
--- a/app/dashboard/api/engine_report/reports_stats.php
+++ b/app/dashboard/api/engine_report/reports_stats.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('dashboard');
 
diff --git a/app/expense/api/engine/convert_purchase_request.php b/app/expense/api/engine/convert_purchase_request.php
index 323aca0..8ba4d99 100644
--- a/app/expense/api/engine/convert_purchase_request.php
+++ b/app/expense/api/engine/convert_purchase_request.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/PurchaseOrderManager.php';
-require '../../../assets/utils/classes/PurchaseRequestManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
+require_once '../../../assets/utils/classes/PurchaseRequestManager.php';
 require_role($user_role, ['owner', 'admin', 'staff']);
 
 $request_id    = (int)($data['request_id']  ?? 0);
diff --git a/app/expense/api/engine/manage_purchase_request.php b/app/expense/api/engine/manage_purchase_request.php
index 71ec5b7..bc6a6bf 100644
--- a/app/expense/api/engine/manage_purchase_request.php
+++ b/app/expense/api/engine/manage_purchase_request.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/PurchaseRequestManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/PurchaseRequestManager.php';
 require_role($user_role, ['owner', 'admin', 'staff']);
 
 $action = $data['action'] ?? '';
diff --git a/app/expense/api/engine/manage_supplier_credit_note.php b/app/expense/api/engine/manage_supplier_credit_note.php
index 2131481..2cf9a9e 100644
--- a/app/expense/api/engine/manage_supplier_credit_note.php
+++ b/app/expense/api/engine/manage_supplier_credit_note.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     try {
         $new_id = null;
diff --git a/app/expense/api/engine/retrieve_purchase_request.php b/app/expense/api/engine/retrieve_purchase_request.php
index 37fd452..b7a98f4 100644
--- a/app/expense/api/engine/retrieve_purchase_request.php
+++ b/app/expense/api/engine/retrieve_purchase_request.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/PurchaseRequestManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/PurchaseRequestManager.php';
 
 $id  = (int)($data['id'] ?? 0);
 $prm = new PurchaseRequestManager($pdo2, $company_id);
diff --git a/app/expense/api/engine/update_purchase_request_status.php b/app/expense/api/engine/update_purchase_request_status.php
index 349b701..01689c2 100644
--- a/app/expense/api/engine/update_purchase_request_status.php
+++ b/app/expense/api/engine/update_purchase_request_status.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/PurchaseRequestManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/PurchaseRequestManager.php';
 require_role($user_role, ['owner', 'admin', 'staff']);
 
 $id     = (int)($data['id']          ?? 0);
diff --git a/app/expense/manage_purchase_invoice.php b/app/expense/manage_purchase_invoice.php
index 324abed..ee3397e 100644
--- a/app/expense/manage_purchase_invoice.php
+++ b/app/expense/manage_purchase_invoice.php
@@ -128,6 +128,10 @@
                 <i class="ti ti-device-floppy me-1"></i>Save
               </button>
 
+              <button class="btn btn-success w-100" id="btn_issue" onclick="issue_invoice()">
+                <i class="ti ti-send me-1"></i>Issue
+              </button>
+
               <a href="#" class="btn btn-outline-info w-100 d-none" id="btn_create_scn">
                 <i class="ti ti-file-minus me-1"></i>Create Supplier Credit Note
               </a>
@@ -136,6 +140,10 @@
                 <i class="ti ti-ban me-1"></i>Void
               </button>
 
+              <button class="btn btn-outline-danger w-100 d-none" id="btn_delete" onclick="delete_invoice()">
+                <i class="ti ti-trash me-1"></i>Delete
+              </button>
+
             </div>
           </div>
 
@@ -147,6 +155,9 @@
   <?php require '../include_ending.php'; ?>
 
   <script>
+
+  const can_delete = ['admin', 'owner'].includes(user_role);
+
   var invoice_id   = <?php echo $invoice_id; ?>;
   var invoice_data = null;
 
@@ -183,8 +194,13 @@
     $('#due_date_row').toggleClass('d-none', is_dn);
     $('#due_date, #notes').prop('disabled', !is_editable);
 
+    $('#btn_issue').html(is_dn
+      ? '<i class="ti ti-send me-1"></i>Issue Supplier Credit Note'
+      : '<i class="ti ti-send me-1"></i>Issue Purchase Invoice');
+
     var not_editable_hint = (!is_pi && !is_dn) ? 'Unsupported document type' : '';
-    set_btn_state('#btn_save', is_editable, not_editable_hint || 'Only draft documents can be edited');
+    set_btn_state('#btn_save',  is_editable, not_editable_hint || 'Only draft documents can be edited');
+    set_btn_state('#btn_issue', is_editable, not_editable_hint || (status > 0 ? 'Already issued' : 'Only drafts can be issued'));
 
     $('#btn_create_scn')
       .toggleClass('d-none', !(is_pi && status >= 1 && status !== 4))
@@ -192,8 +208,10 @@
 
     set_btn_state('#btn_void', is_pi && status >= 1 && status !== 4,
       !is_pi ? 'Only purchase invoices can be voided'
-      : status === 0 ? 'Invoice has not been issued yet'
+      : status === 0 ? 'Issue the document before voiding'
       : status === 4 ? 'Already void' : '');
+
+    $('#btn_delete').toggleClass('d-none', !can_delete || !invoice_id);
   }
 
   function retrieve_invoice() {
@@ -325,6 +343,64 @@
     });
   }
 
+  function issue_invoice() {
+    var is_dn    = invoice_data && invoice_data.doc_type === 'supplier_credit_note';
+    var due_date = $('#due_date').val().trim();
+    if (!is_dn && !due_date) {
+      bootbox.alert('Please enter a due date before issuing this purchase invoice.');
+      return;
+    }
+    var label = is_dn ? 'Issue Supplier Credit Note' : 'Issue Purchase Invoice';
+    bootbox.confirm({
+      message: is_dn ? 'Issue this supplier credit note?' : 'Issue this purchase invoice?',
+      buttons: {
+        confirm: { label: label, className: 'btn-success' },
+        cancel:  { label: 'Back', className: 'btn-secondary' }
+      },
+      callback: function(result) {
+        if (!result) return;
+        ajax_request({
+          url: '<?php echo $server_url?>order/api/engine/issue_invoice.php',
+          autoPrepare: true,
+          checkRequired: 0,
+          action: 'update',
+          data: {
+            invoice_id: invoice_id,
+            due_date: is_dn ? '' : due_date.split('/').reverse().join('-')
+          },
+          onSuccess: function(res) {
+            retrieve_invoice();
+            if (res.gl_posted === true) {
+              toastr.success('GL entry posted automatically.', 'GL Posted');
+            } else if (res.gl_posted === false) {
+              toastr.warning('Document issued, but GL posting failed: ' + (res.gl_message || 'Unknown error'), 'GL Skipped', { timeOut: 8000 });
+            }
+          }
+        });
+      }
+    });
+  }
+
+  function delete_invoice() {
+    bootbox.confirm({
+      message: 'Delete this document? Any GL entry will be removed.',
+      buttons: { confirm: { label: 'Delete', className: 'btn-danger' }, cancel: { label: 'Back', className: 'btn-secondary' } },
+      callback: function(result) {
+        if (!result) return;
+        ajax_request({
+          url: '<?php echo $server_url?>order/api/engine/delete_invoice.php',
+          autoPrepare: false,
+          checkRequired: 0,
+          action: 'delete',
+          data: { id: invoice_id },
+          onSuccess: function() {
+            window.location.href = '<?php echo $server_url?>expense/purchase_invoice.php';
+          }
+        });
+      }
+    });
+  }
+
   function void_invoice() {
     bootbox.confirm({
       message: '<strong>Void this purchase invoice?</strong><br>This action cannot be undone.',
diff --git a/app/expense/purchase_invoice.php b/app/expense/purchase_invoice.php
index 4bf0ecf..9bd2054 100644
--- a/app/expense/purchase_invoice.php
+++ b/app/expense/purchase_invoice.php
@@ -193,6 +193,7 @@
   <script>
   var current_tab = <?php echo json_encode($_GET['tab'] ?? 'purchase_invoice'); ?>;
   var all_invoices = [];
+  const can_delete = ['admin', 'owner'].includes(user_role);
   var formula_map  = {};
 
   function load_formula_map() {
@@ -352,9 +353,7 @@
           <a href="javascript:;" title="View GL Entry" class="me-2" onclick="show_gl_modal('purchase_invoice',${inv.id})">
             <i class="ti ti-book fs-5 text-secondary"></i>
           </a>
-          <a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${inv.id},'${escape_html(inv.invoice_number)}')">
-            <i class="ti ti-trash fs-5"></i>
-          </a>
+          ${can_delete ? `<a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${inv.id},'${escape_html(inv.invoice_number)}')"><i class="ti ti-trash fs-5"></i></a>` : ''}
         </td>
       </tr>`;
     });
@@ -400,9 +399,7 @@
           <a href="javascript:;" title="View GL Entry" class="me-2" onclick="show_gl_modal('supplier_credit_note',${scn.id})">
             <i class="ti ti-book fs-5 text-secondary"></i>
           </a>
-          <a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${scn.id},'${escape_html(scn.invoice_number)}')">
-            <i class="ti ti-trash fs-5"></i>
-          </a>
+          ${can_delete ? `<a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${scn.id},'${escape_html(scn.invoice_number)}')"><i class="ti ti-trash fs-5"></i></a>` : ''}
         </td>
       </tr>`;
     });
diff --git a/app/finance/api/engine/delete_payment.php b/app/finance/api/engine/delete_payment.php
index 3538a5f..db37bd6 100644
--- a/app/finance/api/engine/delete_payment.php
+++ b/app/finance/api/engine/delete_payment.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/PaymentManager.php';
+require_once '../../../assets/utils/classes/PaymentManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/finance/api/engine/delete_payment_billing.php b/app/finance/api/engine/delete_payment_billing.php
index d288c41..c51d52f 100644
--- a/app/finance/api/engine/delete_payment_billing.php
+++ b/app/finance/api/engine/delete_payment_billing.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/PaymentBillingManager.php';
+require_once '../../../assets/utils/classes/PaymentBillingManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/finance/api/engine/delete_receipt.php b/app/finance/api/engine/delete_receipt.php
index cf992a6..1deee8a 100644
--- a/app/finance/api/engine/delete_receipt.php
+++ b/app/finance/api/engine/delete_receipt.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/ReceiptManager.php';
+require_once '../../../assets/utils/classes/ReceiptManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/finance/api/engine/delete_receipt_billing.php b/app/finance/api/engine/delete_receipt_billing.php
index 3b7cf20..262ea0d 100644
--- a/app/finance/api/engine/delete_receipt_billing.php
+++ b/app/finance/api/engine/delete_receipt_billing.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/ReceiptBillingManager.php';
+require_once '../../../assets/utils/classes/ReceiptBillingManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/finance/api/engine/manage_payment.php b/app/finance/api/engine/manage_payment.php
index c5c95a7..38d5d81 100644
--- a/app/finance/api/engine/manage_payment.php
+++ b/app/finance/api/engine/manage_payment.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/PaymentManager.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/PaymentManager.php';
 
     try {
         $mgr = new PaymentManager($pdo2, $company_id);
diff --git a/app/finance/api/engine/manage_payment_billing.php b/app/finance/api/engine/manage_payment_billing.php
index fa174b4..23b4992 100644
--- a/app/finance/api/engine/manage_payment_billing.php
+++ b/app/finance/api/engine/manage_payment_billing.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/PaymentBillingManager.php';
+    require_once '../../../assets/utils/classes/PaymentBillingManager.php';
 
     try {
         $mgr = new PaymentBillingManager($pdo2, $company_id);
diff --git a/app/finance/api/engine/manage_receipt.php b/app/finance/api/engine/manage_receipt.php
index 09671aa..6f65d8d 100644
--- a/app/finance/api/engine/manage_receipt.php
+++ b/app/finance/api/engine/manage_receipt.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/ReceiptManager.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/ReceiptManager.php';
 
     try {
         $mgr = new ReceiptManager($pdo2, $company_id);
diff --git a/app/finance/api/engine/manage_receipt_billing.php b/app/finance/api/engine/manage_receipt_billing.php
index e605f74..197d559 100644
--- a/app/finance/api/engine/manage_receipt_billing.php
+++ b/app/finance/api/engine/manage_receipt_billing.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/ReceiptBillingManager.php';
+    require_once '../../../assets/utils/classes/ReceiptBillingManager.php';
 
     try {
         $mgr = new ReceiptBillingManager($pdo2, $company_id);
diff --git a/app/ics/api/engine/approve_stock.php b/app/ics/api/engine/approve_stock.php
index 496a403..d181aa0 100644
--- a/app/ics/api/engine/approve_stock.php
+++ b/app/ics/api/engine/approve_stock.php
@@ -12,9 +12,9 @@
  *   type         string  'in' | 'out' | 'transfer'
  */
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/StockManager.php';
-require '../../../assets/utils/classes/WarehouseManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/StockManager.php';
+require_once '../../../assets/utils/classes/WarehouseManager.php';
 
 require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/ics/api/engine/barcode_lookup.php b/app/ics/api/engine/barcode_lookup.php
index 2a33cd6..6db0793 100644
--- a/app/ics/api/engine/barcode_lookup.php
+++ b/app/ics/api/engine/barcode_lookup.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
-    require '../../../assets/utils/classes/BarcodeManager.php';
+    require_once '../../../assets/utils/classes/BarcodeManager.php';
 
     $barcode = trim($data['barcode'] ?? '');
 
diff --git a/app/ics/api/engine/contact_search.php b/app/ics/api/engine/contact_search.php
index aad19de..34cd88e 100644
--- a/app/ics/api/engine/contact_search.php
+++ b/app/ics/api/engine/contact_search.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ContactManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ContactManager.php';
 
     $contact = new ContactManager($pdo2, $company_id);
     $answer['result']  = $contact->searchContact($data['keyword'] ?? '');
diff --git a/app/ics/api/engine/delete_stock_in.php b/app/ics/api/engine/delete_stock_in.php
index 33ab892..144fd2d 100644
--- a/app/ics/api/engine/delete_stock_in.php
+++ b/app/ics/api/engine/delete_stock_in.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/ics/api/engine/delete_stock_out.php b/app/ics/api/engine/delete_stock_out.php
index 9b0d720..2d48838 100644
--- a/app/ics/api/engine/delete_stock_out.php
+++ b/app/ics/api/engine/delete_stock_out.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/ics/api/engine/delete_stock_transfer.php b/app/ics/api/engine/delete_stock_transfer.php
index a14bb3c..3a97103 100644
--- a/app/ics/api/engine/delete_stock_transfer.php
+++ b/app/ics/api/engine/delete_stock_transfer.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/ics/api/engine/location_barcode_label.php b/app/ics/api/engine/location_barcode_label.php
index 1d2e743..8b5e21a 100644
--- a/app/ics/api/engine/location_barcode_label.php
+++ b/app/ics/api/engine/location_barcode_label.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/BarcodeManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/BarcodeManager.php';
 
     $label_action = $data['label_action'] ?? 'create';
     $barcode      = trim($data['barcode'] ?? '');
diff --git a/app/ics/api/engine/manage_stock_in.php b/app/ics/api/engine/manage_stock_in.php
index aa099ca..8e0706b 100644
--- a/app/ics/api/engine/manage_stock_in.php
+++ b/app/ics/api/engine/manage_stock_in.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/StockManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
         require_role($user_role, ['owner', 'admin', 'staff']);
diff --git a/app/ics/api/engine/manage_stock_out.php b/app/ics/api/engine/manage_stock_out.php
index 5669e03..0d750d6 100644
--- a/app/ics/api/engine/manage_stock_out.php
+++ b/app/ics/api/engine/manage_stock_out.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/StockManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
         require_role($user_role, ['owner', 'admin', 'staff']);
diff --git a/app/ics/api/engine/manage_stock_transfer.php b/app/ics/api/engine/manage_stock_transfer.php
index 6826e83..2afc44b 100644
--- a/app/ics/api/engine/manage_stock_transfer.php
+++ b/app/ics/api/engine/manage_stock_transfer.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/StockManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
         require_role($user_role, ['owner', 'admin', 'staff']);
diff --git a/app/ics/api/engine/product_search.php b/app/ics/api/engine/product_search.php
index 008018d..af9c3b2 100644
--- a/app/ics/api/engine/product_search.php
+++ b/app/ics/api/engine/product_search.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     $product = new ProductManager($pdo2, $company_id);
     $answer['result']  = $product->searchProduct($data['keyword'] ?? '');
diff --git a/app/ics/api/engine/retrieve_active_lot.php b/app/ics/api/engine/retrieve_active_lot.php
index 98976ff..2f6c351 100644
--- a/app/ics/api/engine/retrieve_active_lot.php
+++ b/app/ics/api/engine/retrieve_active_lot.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $product_sku = $data['product_sku'] ?? '';
 
diff --git a/app/ics/api/engine/retrieve_active_serial.php b/app/ics/api/engine/retrieve_active_serial.php
index 9d97c6c..c8b1efb 100644
--- a/app/ics/api/engine/retrieve_active_serial.php
+++ b/app/ics/api/engine/retrieve_active_serial.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $product_sku = $data['product_sku'] ?? '';
 
diff --git a/app/ics/api/engine/retrieve_aisle.php b/app/ics/api/engine/retrieve_aisle.php
index 9d175dd..3608a1d 100644
--- a/app/ics/api/engine/retrieve_aisle.php
+++ b/app/ics/api/engine/retrieve_aisle.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $type    = $data['type'] ?? '';
     $whMgmt  = new WarehouseManager($pdo2, $company_id);
diff --git a/app/ics/api/engine/retrieve_lot.php b/app/ics/api/engine/retrieve_lot.php
index c343f6d..23cb109 100644
--- a/app/ics/api/engine/retrieve_lot.php
+++ b/app/ics/api/engine/retrieve_lot.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh = new WarehouseManager($pdo2, $company_id);
     $answer['result']  = $wh->getLotList(
diff --git a/app/ics/api/engine/retrieve_rack.php b/app/ics/api/engine/retrieve_rack.php
index fc625a0..deda264 100644
--- a/app/ics/api/engine/retrieve_rack.php
+++ b/app/ics/api/engine/retrieve_rack.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $type    = $data['type'] ?? '';
     $whMgmt  = new WarehouseManager($pdo2, $company_id);
diff --git a/app/ics/api/engine/retrieve_stock_by_source.php b/app/ics/api/engine/retrieve_stock_by_source.php
index 1447161..df47eef 100644
--- a/app/ics/api/engine/retrieve_stock_by_source.php
+++ b/app/ics/api/engine/retrieve_stock_by_source.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockSourceManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockSourceManager.php';
 
     try {
         $mgr = new StockSourceManager($pdo2, $company_id);
diff --git a/app/ics/api/engine/retrieve_stock_in.php b/app/ics/api/engine/retrieve_stock_in.php
index 97c2e3d..4ce56f5 100644
--- a/app/ics/api/engine/retrieve_stock_in.php
+++ b/app/ics/api/engine/retrieve_stock_in.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getStockInById((int)$data['wh'], (int)$data['id']);
diff --git a/app/ics/api/engine/retrieve_stock_out.php b/app/ics/api/engine/retrieve_stock_out.php
index 12b1e99..42a9b5a 100644
--- a/app/ics/api/engine/retrieve_stock_out.php
+++ b/app/ics/api/engine/retrieve_stock_out.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getStockOutById((int)$data['wh'], (int)$data['id']);
diff --git a/app/ics/api/engine/retrieve_stock_transfer.php b/app/ics/api/engine/retrieve_stock_transfer.php
index 2c37870..4caba54 100644
--- a/app/ics/api/engine/retrieve_stock_transfer.php
+++ b/app/ics/api/engine/retrieve_stock_transfer.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getTransferById((int)$data['wh'], (int)$data['id']);
diff --git a/app/ics/api/engine/retrieve_warehouse.php b/app/ics/api/engine/retrieve_warehouse.php
index 4fcab1f..357264b 100644
--- a/app/ics/api/engine/retrieve_warehouse.php
+++ b/app/ics/api/engine/retrieve_warehouse.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh       = new WarehouseManager($pdo2, $company_id);
     $type     = $data['type']        ?? '';
diff --git a/app/ics/api/engine/retrieve_zone.php b/app/ics/api/engine/retrieve_zone.php
index 38b08a6..85cf588 100644
--- a/app/ics/api/engine/retrieve_zone.php
+++ b/app/ics/api/engine/retrieve_zone.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $type    = $data['type'] ?? '';
     $whMgmt  = new WarehouseManager($pdo2, $company_id);
diff --git a/app/ics/api/engine/sku_barcode_label.php b/app/ics/api/engine/sku_barcode_label.php
index ca1eeec..abf38a3 100644
--- a/app/ics/api/engine/sku_barcode_label.php
+++ b/app/ics/api/engine/sku_barcode_label.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/BarcodeManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/BarcodeManager.php';
 
     $label_action = $data['label_action'] ?? 'read';
     $product_sku  = trim($data['product_sku'] ?? '');
diff --git a/app/ics/api/engine/sku_label_lots.php b/app/ics/api/engine/sku_label_lots.php
index cac45f8..0732dce 100644
--- a/app/ics/api/engine/sku_label_lots.php
+++ b/app/ics/api/engine/sku_label_lots.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/BarcodeManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/BarcodeManager.php';
 
     $bm = new BarcodeManager($pdo2, $company_id);
 
diff --git a/app/ics/api/engine/sku_label_products.php b/app/ics/api/engine/sku_label_products.php
index 23ed628..2e0076b 100644
--- a/app/ics/api/engine/sku_label_products.php
+++ b/app/ics/api/engine/sku_label_products.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/BarcodeManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/BarcodeManager.php';
 
     $bm = new BarcodeManager($pdo2, $company_id);
 
diff --git a/app/ics/api/engine/stock_in.php b/app/ics/api/engine/stock_in.php
index 2b68f12..d1729a0 100644
--- a/app/ics/api/engine/stock_in.php
+++ b/app/ics/api/engine/stock_in.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getStockList((int)$data['warehouse'], 'in');
diff --git a/app/ics/api/engine/stock_out.php b/app/ics/api/engine/stock_out.php
index 8621e2c..98fcfae 100644
--- a/app/ics/api/engine/stock_out.php
+++ b/app/ics/api/engine/stock_out.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getStockList((int)$data['warehouse'], 'out');
diff --git a/app/ics/api/engine/stock_transfer.php b/app/ics/api/engine/stock_transfer.php
index a5f31f2..d139505 100644
--- a/app/ics/api/engine/stock_transfer.php
+++ b/app/ics/api/engine/stock_transfer.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
 
     $stock = new StockManager($pdo2, $company_id);
     $answer['output']  = $stock->getStockList((int)$data['warehouse'], 'transfer');
diff --git a/app/ics/api/engine/validate_scan_location.php b/app/ics/api/engine/validate_scan_location.php
index 4ca465a..46d70c0 100644
--- a/app/ics/api/engine/validate_scan_location.php
+++ b/app/ics/api/engine/validate_scan_location.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin', 'staff']);
 
diff --git a/app/ics/api/engine_report/product_stats.php b/app/ics/api/engine_report/product_stats.php
index 10130b5..1fa8b04 100644
--- a/app/ics/api/engine_report/product_stats.php
+++ b/app/ics/api/engine_report/product_stats.php
@@ -1,8 +1,8 @@
 <?php 
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/ics/api/engine_report/stock_activity.php b/app/ics/api/engine_report/stock_activity.php
index b6e33ed..2a91ab0 100644
--- a/app/ics/api/engine_report/stock_activity.php
+++ b/app/ics/api/engine_report/stock_activity.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $answer['output'] = $report->getWarehouseActivity((int)$data['warehouse']);
diff --git a/app/ics/api/engine_report/stock_movement.php b/app/ics/api/engine_report/stock_movement.php
index 15bc94d..68c2528 100644
--- a/app/ics/api/engine_report/stock_movement.php
+++ b/app/ics/api/engine_report/stock_movement.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $answer['output']  = $report->getWarehouseStockMovement((int)$data['warehouse']);
diff --git a/app/ics/api/engine_report/stock_trend.php b/app/ics/api/engine_report/stock_trend.php
index 7add337..7a4ac19 100644
--- a/app/ics/api/engine_report/stock_trend.php
+++ b/app/ics/api/engine_report/stock_trend.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $answer['output']  = $report->getWarehouseStockTrend((int)$data['warehouse']);
diff --git a/app/ics/api/engine_report/warehouse_balance.php b/app/ics/api/engine_report/warehouse_balance.php
index 33ece80..de51951 100644
--- a/app/ics/api/engine_report/warehouse_balance.php
+++ b/app/ics/api/engine_report/warehouse_balance.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $answer['output']  = $report->getWarehouseBalanceSummary();
diff --git a/app/ics/api/engine_report/warehouse_overview.php b/app/ics/api/engine_report/warehouse_overview.php
index 4498dc4..51af305 100644
--- a/app/ics/api/engine_report/warehouse_overview.php
+++ b/app/ics/api/engine_report/warehouse_overview.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $warehouse_id = (int)($data['warehouse'] ?? 0);
 
diff --git a/app/ics/api/engine_report/warehouse_stats.php b/app/ics/api/engine_report/warehouse_stats.php
index dfe768a..0415372 100644
--- a/app/ics/api/engine_report/warehouse_stats.php
+++ b/app/ics/api/engine_report/warehouse_stats.php
@@ -1,8 +1,8 @@
 <?php 
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/inventory/api/engine/manage_category.php b/app/inventory/api/engine/manage_category.php
index dda221d..21380d0 100644
--- a/app/inventory/api/engine/manage_category.php
+++ b/app/inventory/api/engine/manage_category.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/manage_product.php b/app/inventory/api/engine/manage_product.php
index 6478619..43388b7 100644
--- a/app/inventory/api/engine/manage_product.php
+++ b/app/inventory/api/engine/manage_product.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/FileUploader.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/FileUploader.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/manage_storage.php b/app/inventory/api/engine/manage_storage.php
index e6105dc..5368238 100644
--- a/app/inventory/api/engine/manage_storage.php
+++ b/app/inventory/api/engine/manage_storage.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     require_role($user_role, ['owner', 'admin']);
diff --git a/app/inventory/api/engine/manage_warehouse.php b/app/inventory/api/engine/manage_warehouse.php
index 0aea4b4..21b3365 100644
--- a/app/inventory/api/engine/manage_warehouse.php
+++ b/app/inventory/api/engine/manage_warehouse.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/manager.php b/app/inventory/api/engine/manager.php
index d03fa9e..c7ccd1f 100644
--- a/app/inventory/api/engine/manager.php
+++ b/app/inventory/api/engine/manager.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/product.php b/app/inventory/api/engine/product.php
index 30d7bf0..0816ea7 100644
--- a/app/inventory/api/engine/product.php
+++ b/app/inventory/api/engine/product.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     $product = new ProductManager($pdo2, $company_id);
     $answer['output']  = $product->getProductList();
diff --git a/app/inventory/api/engine/product_category.php b/app/inventory/api/engine/product_category.php
index 1978e8b..2f4b31c 100644
--- a/app/inventory/api/engine/product_category.php
+++ b/app/inventory/api/engine/product_category.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     $product = new ProductManager($pdo2, $company_id);
     $answer['output']  = $product->getCategoryList();
diff --git a/app/inventory/api/engine/product_stats.php b/app/inventory/api/engine/product_stats.php
index 3e35c90..9daf0b4 100644
--- a/app/inventory/api/engine/product_stats.php
+++ b/app/inventory/api/engine/product_stats.php
@@ -1,8 +1,8 @@
 <?php 
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/inventory/api/engine/remove_category.php b/app/inventory/api/engine/remove_category.php
index 25692bd..7e908b6 100644
--- a/app/inventory/api/engine/remove_category.php
+++ b/app/inventory/api/engine/remove_category.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/remove_product.php b/app/inventory/api/engine/remove_product.php
index c77bbf3..ac5d61a 100644
--- a/app/inventory/api/engine/remove_product.php
+++ b/app/inventory/api/engine/remove_product.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/remove_storage.php b/app/inventory/api/engine/remove_storage.php
index 892ffef..ac7cb41 100644
--- a/app/inventory/api/engine/remove_storage.php
+++ b/app/inventory/api/engine/remove_storage.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/remove_warehouse.php b/app/inventory/api/engine/remove_warehouse.php
index d792651..e6cc7fe 100644
--- a/app/inventory/api/engine/remove_warehouse.php
+++ b/app/inventory/api/engine/remove_warehouse.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     require_role($user_role, ['owner', 'admin']);
 
diff --git a/app/inventory/api/engine/retrieve_category.php b/app/inventory/api/engine/retrieve_category.php
index 14dd4a0..693262e 100644
--- a/app/inventory/api/engine/retrieve_category.php
+++ b/app/inventory/api/engine/retrieve_category.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     $product = new ProductManager($pdo2, $company_id);
     $answer['output']  = $product->getCategoryById((int)$data['id']);
diff --git a/app/inventory/api/engine/retrieve_product.php b/app/inventory/api/engine/retrieve_product.php
index af23869..c90e70d 100644
--- a/app/inventory/api/engine/retrieve_product.php
+++ b/app/inventory/api/engine/retrieve_product.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ProductManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ProductManager.php';
 
     $product = new ProductManager($pdo2, $company_id);
     $answer['output']  = $product->getProductById((int)$data['id']);
diff --git a/app/inventory/api/engine/retrieve_storage.php b/app/inventory/api/engine/retrieve_storage.php
index b91cc4e..836d4e9 100644
--- a/app/inventory/api/engine/retrieve_storage.php
+++ b/app/inventory/api/engine/retrieve_storage.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh = new WarehouseManager($pdo2, $company_id);
     $answer['output']  = $wh->getStorageById((int)$data['id']);
diff --git a/app/inventory/api/engine/retrieve_warehouse.php b/app/inventory/api/engine/retrieve_warehouse.php
index 3fefb8a..cf178ed 100644
--- a/app/inventory/api/engine/retrieve_warehouse.php
+++ b/app/inventory/api/engine/retrieve_warehouse.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh = new WarehouseManager($pdo2, $company_id);
     $answer['output']  = $wh->getWarehouseById((int)$data['id']);
diff --git a/app/inventory/api/engine/storage.php b/app/inventory/api/engine/storage.php
index 9beb265..7ace205 100644
--- a/app/inventory/api/engine/storage.php
+++ b/app/inventory/api/engine/storage.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh = new WarehouseManager($pdo2, $company_id);
     $answer['output']  = $wh->getStorageList();
diff --git a/app/inventory/api/engine/warehouse.php b/app/inventory/api/engine/warehouse.php
index 7e98cba..eeb2049 100644
--- a/app/inventory/api/engine/warehouse.php
+++ b/app/inventory/api/engine/warehouse.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $wh = new WarehouseManager($pdo2, $company_id);
     $answer['output'] = $wh->getWarehouseListAll();
diff --git a/app/inventory/api/engine/warehouse_stats.php b/app/inventory/api/engine/warehouse_stats.php
index a9a8b9c..47aca07 100644
--- a/app/inventory/api/engine/warehouse_stats.php
+++ b/app/inventory/api/engine/warehouse_stats.php
@@ -1,8 +1,8 @@
 <?php 
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/login/api/engine/back.php b/app/login/api/engine/back.php
index 19442f5..7ada439 100644
--- a/app/login/api/engine/back.php
+++ b/app/login/api/engine/back.php
@@ -21,9 +21,9 @@
  *   { "success": 1 }
  */
 
-require '../../../session.php';
+require_once '../../../session.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 // Intentional 1-second delay — prevents timing attacks on session enumeration
 sleep(1);
diff --git a/app/login/api/engine/invited_onboarding.php b/app/login/api/engine/invited_onboarding.php
index a74205b..ab262a4 100644
--- a/app/login/api/engine/invited_onboarding.php
+++ b/app/login/api/engine/invited_onboarding.php
@@ -23,12 +23,12 @@
  *   10. Return { success: 1 }.
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../preset.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../preset.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/PasswordManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/PasswordManager.php';
 
 header('Content-Type: application/json; charset=utf-8');
 
diff --git a/app/login/api/engine/login_confirm.php b/app/login/api/engine/login_confirm.php
index c57999c..2317c50 100644
--- a/app/login/api/engine/login_confirm.php
+++ b/app/login/api/engine/login_confirm.php
@@ -48,11 +48,11 @@
  *   On failure:  { "message": "Wrong OTP! Please try again. (Our OTP is valid for 5 minute)" }
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../preset.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../preset.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 // ── Step 1: Load session state written by login_otp.php ───────────────────────
 $data["username"] = $_SESSION["login_data"]['username'];
diff --git a/app/login/api/engine/login_otp.php b/app/login/api/engine/login_otp.php
index d4c4760..6b29429 100644
--- a/app/login/api/engine/login_otp.php
+++ b/app/login/api/engine/login_otp.php
@@ -57,11 +57,11 @@
  *                { "expire": "expire" } — licence has expired
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../preset.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../preset.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 // ── Step 1: Resolve user_id from username or email (case-insensitive) ────────
 $sth = $pdo1->prepare("select user_id from user where ? in (username,email) ");
diff --git a/app/login/api/engine/onboarding.php b/app/login/api/engine/onboarding.php
index a6d7e70..84e4636 100644
--- a/app/login/api/engine/onboarding.php
+++ b/app/login/api/engine/onboarding.php
@@ -48,10 +48,10 @@
  *   On failure:  { "success": 0, "message": "<reason>" }
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../dbconn.php';
-require '../../../assets/utils/db_helpers.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../dbconn.php';
+require_once '../../../assets/utils/db_helpers.php';
 
 header('Content-Type: application/json; charset=utf-8');
 
diff --git a/app/login/api/engine/register.php b/app/login/api/engine/register.php
index d3739c5..b49fab2 100644
--- a/app/login/api/engine/register.php
+++ b/app/login/api/engine/register.php
@@ -43,11 +43,11 @@
  *   On failure:  { "success": 0, "message": "<reason>" }
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../dbconn.php';
-require '../../../assets/utils/db_helpers.php';
-require '../../../assets/utils/classes/PasswordManager.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../dbconn.php';
+require_once '../../../assets/utils/db_helpers.php';
+require_once '../../../assets/utils/classes/PasswordManager.php';
 
 header('Content-Type: application/json; charset=utf-8');
 
diff --git a/app/login/api/engine/request_new_otp.php b/app/login/api/engine/request_new_otp.php
index 97603a7..1bdd312 100644
--- a/app/login/api/engine/request_new_otp.php
+++ b/app/login/api/engine/request_new_otp.php
@@ -42,11 +42,11 @@
  *   On failure:  { "message": "Incorrect Password" }
  */
 
-require '../../../session.php';
-require '../../../config.php';
-require '../../../preset.php';
+require_once '../../../session.php';
+require_once '../../../config.php';
+require_once '../../../preset.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 // ── Step 1: Reload credentials from session ───────────────────────────────────
 // These were stored by login_otp.php so the user doesn't have to retype them.
diff --git a/app/login/api/engine/request_reset_otp.php b/app/login/api/engine/request_reset_otp.php
index c52b36f..22dcade 100644
--- a/app/login/api/engine/request_reset_otp.php
+++ b/app/login/api/engine/request_reset_otp.php
@@ -1,8 +1,8 @@
 <?php
 
-require '../../../session.php';
+require_once '../../../session.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 // Resolve user by username or email
 $identifier = strtolower(trim($data['identifier'] ?? ''));
diff --git a/app/login/api/engine/reset_password_otp.php b/app/login/api/engine/reset_password_otp.php
index 1fa85c1..16cd3ac 100644
--- a/app/login/api/engine/reset_password_otp.php
+++ b/app/login/api/engine/reset_password_otp.php
@@ -1,8 +1,8 @@
 <?php
 
-require '../../../session.php';
+require_once '../../../session.php';
 define('UNAUTHENTICATED_ROUTE', true);
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 
 if (empty($_SESSION['reset_user_id'])) {
     http_response_code(400);
diff --git a/app/order/api/engine/cancel_order.php b/app/order/api/engine/cancel_order.php
index db1b272..4680e90 100644
--- a/app/order/api/engine/cancel_order.php
+++ b/app/order/api/engine/cancel_order.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin']);
-    require '../../../assets/utils/classes/OrderManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/order/api/engine/cancel_return.php b/app/order/api/engine/cancel_return.php
index 9593437..479fe54 100644
--- a/app/order/api/engine/cancel_return.php
+++ b/app/order/api/engine/cancel_return.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin']);
-    require '../../../assets/utils/classes/ReturnManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/ReturnManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/order/api/engine/confirm_order.php b/app/order/api/engine/confirm_order.php
index 359c148..a11d1f5 100644
--- a/app/order/api/engine/confirm_order.php
+++ b/app/order/api/engine/confirm_order.php
@@ -1,11 +1,11 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/OrderManager.php';
-    require '../../../assets/utils/classes/StockManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $id = (int)($data['id'] ?? 0);
diff --git a/app/order/api/engine/confirm_return.php b/app/order/api/engine/confirm_return.php
index f8d97d5..073ad41 100644
--- a/app/order/api/engine/confirm_return.php
+++ b/app/order/api/engine/confirm_return.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/ReturnManager.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/ReturnManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $id = (int)($data['id'] ?? 0);
diff --git a/app/order/api/engine/delete_invoice.php b/app/order/api/engine/delete_invoice.php
index 516cff3..8b1e618 100644
--- a/app/order/api/engine/delete_invoice.php
+++ b/app/order/api/engine/delete_invoice.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/InvoiceManager.php';
+require_once '../../../assets/utils/classes/InvoiceManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/order/api/engine/delete_order.php b/app/order/api/engine/delete_order.php
index 000f43a..bf983f6 100644
--- a/app/order/api/engine/delete_order.php
+++ b/app/order/api/engine/delete_order.php
@@ -1,9 +1,9 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/OrderManager.php';
-require '../../../assets/utils/classes/WarehouseManager.php';
+require_once '../../../assets/utils/classes/OrderManager.php';
+require_once '../../../assets/utils/classes/WarehouseManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/order/api/engine/delete_return.php b/app/order/api/engine/delete_return.php
index 9efe60a..d4619ac 100644
--- a/app/order/api/engine/delete_return.php
+++ b/app/order/api/engine/delete_return.php
@@ -1,9 +1,9 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/ReturnManager.php';
-require '../../../assets/utils/classes/WarehouseManager.php';
+require_once '../../../assets/utils/classes/ReturnManager.php';
+require_once '../../../assets/utils/classes/WarehouseManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/order/api/engine/issue_invoice.php b/app/order/api/engine/issue_invoice.php
index 2dd074f..717d5bb 100644
--- a/app/order/api/engine/issue_invoice.php
+++ b/app/order/api/engine/issue_invoice.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $id       = (int)($data['id'] ?? ($data['invoice_id'] ?? 0));
     $due_date = trim((string)($data['due_date'] ?? ''));
diff --git a/app/order/api/engine/manage_invoice.php b/app/order/api/engine/manage_invoice.php
index ab1be7e..78b932a 100644
--- a/app/order/api/engine/manage_invoice.php
+++ b/app/order/api/engine/manage_invoice.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     try {
         $action = $data['action'] ?? 'update';
diff --git a/app/order/api/engine/manage_order.php b/app/order/api/engine/manage_order.php
index 4991ed0..48533ba 100644
--- a/app/order/api/engine/manage_order.php
+++ b/app/order/api/engine/manage_order.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
 
     // Decode items JSON string back to array
     $data['items'] = json_decode($data['items'] ?? '[]', true) ?: [];
diff --git a/app/order/api/engine/manage_return.php b/app/order/api/engine/manage_return.php
index d969056..11b0bc0 100644
--- a/app/order/api/engine/manage_return.php
+++ b/app/order/api/engine/manage_return.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/ReturnManager.php';
+    require_once '../../../assets/utils/classes/ReturnManager.php';
 
     $action = $data['action'] ?? 'save';
     $data['items'] = json_decode($data['items'] ?? '[]', true) ?: [];
diff --git a/app/order/api/engine/proceed_to_credit_note.php b/app/order/api/engine/proceed_to_credit_note.php
index e85751b..53e3190 100644
--- a/app/order/api/engine/proceed_to_credit_note.php
+++ b/app/order/api/engine/proceed_to_credit_note.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $return_id = (int)($data['return_id'] ?? 0);
 
diff --git a/app/order/api/engine/proceed_to_invoice.php b/app/order/api/engine/proceed_to_invoice.php
index de074fb..3db1901 100644
--- a/app/order/api/engine/proceed_to_invoice.php
+++ b/app/order/api/engine/proceed_to_invoice.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $order_id = (int)($data['order_id'] ?? 0);
 
diff --git a/app/order/api/engine/retrieve_invoice.php b/app/order/api/engine/retrieve_invoice.php
index 1573701..83fdf12 100644
--- a/app/order/api/engine/retrieve_invoice.php
+++ b/app/order/api/engine/retrieve_invoice.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $inv = new InvoiceManager($pdo2, $company_id);
     $id  = (int)($data['invoice_id'] ?? 0);
diff --git a/app/order/api/engine/retrieve_order.php b/app/order/api/engine/retrieve_order.php
index 9b18857..611652c 100644
--- a/app/order/api/engine/retrieve_order.php
+++ b/app/order/api/engine/retrieve_order.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
 
     $order = new OrderManager($pdo2, $company_id);
 
diff --git a/app/order/api/engine/retrieve_return.php b/app/order/api/engine/retrieve_return.php
index a976920..48f6ccc 100644
--- a/app/order/api/engine/retrieve_return.php
+++ b/app/order/api/engine/retrieve_return.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/ReturnManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/ReturnManager.php';
 
     $ret = new ReturnManager($pdo2, $company_id);
     $id  = (int)($data['id'] ?? 0);
diff --git a/app/order/api/engine/update_invoice_status.php b/app/order/api/engine/update_invoice_status.php
index 51214b6..64fc982 100644
--- a/app/order/api/engine/update_invoice_status.php
+++ b/app/order/api/engine/update_invoice_status.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $id     = (int)($data['invoice_id'] ?? 0);
     $status = (int)($data['status']     ?? 0);
diff --git a/app/order/api/engine/update_order_status.php b/app/order/api/engine/update_order_status.php
index 351e63c..680bbd1 100644
--- a/app/order/api/engine/update_order_status.php
+++ b/app/order/api/engine/update_order_status.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $id                  = (int)($data['id']                  ?? 0);
diff --git a/app/order/api/engine/void_invoice.php b/app/order/api/engine/void_invoice.php
index 9c40710..4f8cc94 100644
--- a/app/order/api/engine/void_invoice.php
+++ b/app/order/api/engine/void_invoice.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/cancel_po.php b/app/po/api/engine/cancel_po.php
index ba59d76..6d308e4 100644
--- a/app/po/api/engine/cancel_po.php
+++ b/app/po/api/engine/cancel_po.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin']);
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/cancel_supplier_return.php b/app/po/api/engine/cancel_supplier_return.php
index 78c74f2..5abdbf6 100644
--- a/app/po/api/engine/cancel_supplier_return.php
+++ b/app/po/api/engine/cancel_supplier_return.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/SupplierReturnManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/SupplierReturnManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
 
     $return_id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/close_po.php b/app/po/api/engine/close_po.php
index c0fcc78..8f8b267 100644
--- a/app/po/api/engine/close_po.php
+++ b/app/po/api/engine/close_po.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/confirm_po.php b/app/po/api/engine/confirm_po.php
index 8fda034..4e680a3 100644
--- a/app/po/api/engine/confirm_po.php
+++ b/app/po/api/engine/confirm_po.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/confirm_supplier_return.php b/app/po/api/engine/confirm_supplier_return.php
index f482413..8dd54e7 100644
--- a/app/po/api/engine/confirm_supplier_return.php
+++ b/app/po/api/engine/confirm_supplier_return.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/SupplierReturnManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/SupplierReturnManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $return_id = (int)($data['id'] ?? 0);
diff --git a/app/po/api/engine/delete_po.php b/app/po/api/engine/delete_po.php
index 82f983f..8d52eb2 100644
--- a/app/po/api/engine/delete_po.php
+++ b/app/po/api/engine/delete_po.php
@@ -1,9 +1,9 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/PurchaseOrderManager.php';
-require '../../../assets/utils/classes/WarehouseManager.php';
+require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
+require_once '../../../assets/utils/classes/WarehouseManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/delete_purchase_request.php b/app/po/api/engine/delete_purchase_request.php
index 2f562d1..ae035a4 100644
--- a/app/po/api/engine/delete_purchase_request.php
+++ b/app/po/api/engine/delete_purchase_request.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/PurchaseRequestManager.php';
+require_once '../../../assets/utils/classes/PurchaseRequestManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/delete_supplier_return.php b/app/po/api/engine/delete_supplier_return.php
index d16be7d..9ec38b2 100644
--- a/app/po/api/engine/delete_supplier_return.php
+++ b/app/po/api/engine/delete_supplier_return.php
@@ -1,9 +1,9 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/SupplierReturnManager.php';
-require '../../../assets/utils/classes/WarehouseManager.php';
+require_once '../../../assets/utils/classes/SupplierReturnManager.php';
+require_once '../../../assets/utils/classes/WarehouseManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/po/api/engine/manage_po.php b/app/po/api/engine/manage_po.php
index cdc57fe..2c89d5e 100644
--- a/app/po/api/engine/manage_po.php
+++ b/app/po/api/engine/manage_po.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/UsageGuard.php';
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $data['items'] = json_decode($data['items'] ?? '[]', true) ?: [];
 
diff --git a/app/po/api/engine/manage_supplier_return.php b/app/po/api/engine/manage_supplier_return.php
index 25ef75e..20bc67c 100644
--- a/app/po/api/engine/manage_supplier_return.php
+++ b/app/po/api/engine/manage_supplier_return.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/SupplierReturnManager.php';
+    require_once '../../../assets/utils/classes/SupplierReturnManager.php';
 
     $mgr = new SupplierReturnManager($pdo2, $company_id);
 
diff --git a/app/po/api/engine/proceed_to_purchase_invoice.php b/app/po/api/engine/proceed_to_purchase_invoice.php
index 6b3f7bf..e8cb9c6 100644
--- a/app/po/api/engine/proceed_to_purchase_invoice.php
+++ b/app/po/api/engine/proceed_to_purchase_invoice.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $po_id = (int)($data['po_id'] ?? 0);
 
diff --git a/app/po/api/engine/proceed_to_supplier_credit_note.php b/app/po/api/engine/proceed_to_supplier_credit_note.php
index f0f80f4..8ddccf4 100644
--- a/app/po/api/engine/proceed_to_supplier_credit_note.php
+++ b/app/po/api/engine/proceed_to_supplier_credit_note.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $return_id = (int)($data['return_id'] ?? 0);
 
diff --git a/app/po/api/engine/receive_po.php b/app/po/api/engine/receive_po.php
index 49afc0d..edda012 100644
--- a/app/po/api/engine/receive_po.php
+++ b/app/po/api/engine/receive_po.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
-    require '../../../assets/utils/classes/StockManager.php';
-    require '../../../assets/utils/classes/WarehouseManager.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/StockManager.php';
+    require_once '../../../assets/utils/classes/WarehouseManager.php';
     require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
     $id = (int)($data['id'] ?? 0);
diff --git a/app/po/api/engine/retrieve_po.php b/app/po/api/engine/retrieve_po.php
index 8880e60..2562dbb 100644
--- a/app/po/api/engine/retrieve_po.php
+++ b/app/po/api/engine/retrieve_po.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $po = new PurchaseOrderManager($pdo2, $company_id);
 
diff --git a/app/po/api/engine/retrieve_supplier_return.php b/app/po/api/engine/retrieve_supplier_return.php
index 57a143e..a6aecb2 100644
--- a/app/po/api/engine/retrieve_supplier_return.php
+++ b/app/po/api/engine/retrieve_supplier_return.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/SupplierReturnManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/SupplierReturnManager.php';
 
     $mgr = new SupplierReturnManager($pdo2, $company_id);
     $id  = (int)($data['id'] ?? 0);
diff --git a/app/po/api/engine/update_po_payment.php b/app/po/api/engine/update_po_payment.php
index 9f3834d..c1ad4dd 100644
--- a/app/po/api/engine/update_po_payment.php
+++ b/app/po/api/engine/update_po_payment.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/PurchaseOrderManager.php';
+    require_once '../../../assets/utils/classes/PurchaseOrderManager.php';
 
     $id             = (int)($data['id']             ?? 0);
     $payment_status = (int)($data['payment_status'] ?? 0);
diff --git a/app/reports/api/engine_report/expired_stock.php b/app/reports/api/engine_report/expired_stock.php
index c0381af..42d8474 100644
--- a/app/reports/api/engine_report/expired_stock.php
+++ b/app/reports/api/engine_report/expired_stock.php
@@ -1,11 +1,11 @@
 <?php
     session_start();
 
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
 
diff --git a/app/reports/api/engine_report/lot_stock_log.php b/app/reports/api/engine_report/lot_stock_log.php
index 03d4c56..acb1fdb 100644
--- a/app/reports/api/engine_report/lot_stock_log.php
+++ b/app/reports/api/engine_report/lot_stock_log.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $answer['output']  = $report->getLotStockLog(
diff --git a/app/reports/api/engine_report/product_lot.php b/app/reports/api/engine_report/product_lot.php
index 251b8d4..854a708 100644
--- a/app/reports/api/engine_report/product_lot.php
+++ b/app/reports/api/engine_report/product_lot.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report = new ReportManager($pdo2, $company_id);
     $result = $report->getProductLots();
diff --git a/app/reports/api/engine_report/rack_log.php b/app/reports/api/engine_report/rack_log.php
index 9070744..e7790a5 100644
--- a/app/reports/api/engine_report/rack_log.php
+++ b/app/reports/api/engine_report/rack_log.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $rack_id = (int)($data['rack_id'] ?? 0);
 
diff --git a/app/reports/api/engine_report/rack_occupancy.php b/app/reports/api/engine_report/rack_occupancy.php
index effdb5d..443af1d 100644
--- a/app/reports/api/engine_report/rack_occupancy.php
+++ b/app/reports/api/engine_report/rack_occupancy.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $report   = new ReportManager($pdo2, $company_id);
     $total    = $report->getTotalCapacity();
diff --git a/app/reports/api/engine_report/stock_movement.php b/app/reports/api/engine_report/stock_movement.php
index 2b00b78..cdbf678 100644
--- a/app/reports/api/engine_report/stock_movement.php
+++ b/app/reports/api/engine_report/stock_movement.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $data         = json_decode($_POST['json'] ?? '{}', true) ?: [];
     $warehouse_id = (int)($data['warehouse_id'] ?? 0);
diff --git a/app/reports/api/engine_report/stock_movement_sku.php b/app/reports/api/engine_report/stock_movement_sku.php
index 231ecf8..3815843 100644
--- a/app/reports/api/engine_report/stock_movement_sku.php
+++ b/app/reports/api/engine_report/stock_movement_sku.php
@@ -1,10 +1,10 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UsageGuard.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UsageGuard.php';
 
     (new UsageGuard($pdo1, $company_id, $packages))->assertFeatureAccessible('reports');
-    require '../../../assets/utils/classes/ReportManager.php';
+    require_once '../../../assets/utils/classes/ReportManager.php';
 
     $data         = json_decode($_POST['json'] ?? '{}', true) ?: [];
     $warehouse_id = (int)($data['warehouse_id'] ?? 0);
diff --git a/app/revenue/api/engine/convert_quotation.php b/app/revenue/api/engine/convert_quotation.php
index aed2cdd..e7ff6e8 100644
--- a/app/revenue/api/engine/convert_quotation.php
+++ b/app/revenue/api/engine/convert_quotation.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/OrderManager.php';
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/OrderManager.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 require_role($user_role, ['owner', 'admin', 'staff']);
 
diff --git a/app/revenue/api/engine/delete_quotation.php b/app/revenue/api/engine/delete_quotation.php
index 86a4814..7730f94 100644
--- a/app/revenue/api/engine/delete_quotation.php
+++ b/app/revenue/api/engine/delete_quotation.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 $id = (int)($data['id'] ?? 0);
 
diff --git a/app/revenue/api/engine/manage_credit_note.php b/app/revenue/api/engine/manage_credit_note.php
index 2937d22..c237224 100644
--- a/app/revenue/api/engine/manage_credit_note.php
+++ b/app/revenue/api/engine/manage_credit_note.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     try {
         $new_id = null;
diff --git a/app/revenue/api/engine/manage_order.php b/app/revenue/api/engine/manage_order.php
index 90b416c..536afa3 100644
--- a/app/revenue/api/engine/manage_order.php
+++ b/app/revenue/api/engine/manage_order.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/UsageGuard.php';
-require '../../../assets/utils/classes/OrderManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/classes/OrderManager.php';
 
 require_role($user_role, ['owner', 'admin', 'staff']);
 
diff --git a/app/revenue/api/engine/manage_quotation.php b/app/revenue/api/engine/manage_quotation.php
index c286c92..c84fb8a 100644
--- a/app/revenue/api/engine/manage_quotation.php
+++ b/app/revenue/api/engine/manage_quotation.php
@@ -1,8 +1,8 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/UsageGuard.php';
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/UsageGuard.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 $action = $data['action'] ?? '';
 $id     = (int)($data['id'] ?? 0);
diff --git a/app/revenue/api/engine/proceed_to_invoice.php b/app/revenue/api/engine/proceed_to_invoice.php
index 4a9e8f3..7e32d39 100644
--- a/app/revenue/api/engine/proceed_to_invoice.php
+++ b/app/revenue/api/engine/proceed_to_invoice.php
@@ -1,9 +1,9 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/db_auth.php';
     require_role($user_role, ['owner', 'admin', 'staff']);
-    require '../../../assets/utils/classes/OrderManager.php';
-    require '../../../assets/utils/classes/InvoiceManager.php';
+    require_once '../../../assets/utils/classes/OrderManager.php';
+    require_once '../../../assets/utils/classes/InvoiceManager.php';
 
     $order_id = (int)($data['order_id'] ?? 0);
 
diff --git a/app/revenue/api/engine/quotation_stats.php b/app/revenue/api/engine/quotation_stats.php
index 6f6a0bd..80d6644 100644
--- a/app/revenue/api/engine/quotation_stats.php
+++ b/app/revenue/api/engine/quotation_stats.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 try {
     $quotation = new QuotationManager($pdo2, $company_id);
diff --git a/app/revenue/api/engine/retrieve_quotation.php b/app/revenue/api/engine/retrieve_quotation.php
index 068afe0..0102fc2 100644
--- a/app/revenue/api/engine/retrieve_quotation.php
+++ b/app/revenue/api/engine/retrieve_quotation.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 $id = (int)($data['id'] ?? 0);
 $qm = new QuotationManager($pdo2, $company_id);
diff --git a/app/revenue/api/engine/update_quotation_status.php b/app/revenue/api/engine/update_quotation_status.php
index 64e68dc..94c8d5b 100644
--- a/app/revenue/api/engine/update_quotation_status.php
+++ b/app/revenue/api/engine/update_quotation_status.php
@@ -1,7 +1,7 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/QuotationManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/QuotationManager.php';
 
 require_role($user_role, ['owner', 'admin', 'staff']);
 
diff --git a/app/revenue/invoice.php b/app/revenue/invoice.php
index f6a09b7..1666e7a 100644
--- a/app/revenue/invoice.php
+++ b/app/revenue/invoice.php
@@ -194,6 +194,7 @@
   var current_tab = <?php echo json_encode($_GET['tab'] ?? 'invoice'); ?>;
   var all_invoices = [];
   var formula_map  = {};
+  const can_delete = ['admin', 'owner'].includes(user_role);
 
   function is_invoice_overdue(status, due_date) {
     if (String(status) !== '1' || !due_date) return false;
@@ -362,9 +363,7 @@
           <a href="javascript:;" title="View GL Entry" class="me-2" onclick="show_gl_modal('invoice',${inv.id})">
             <i class="ti ti-book fs-5 text-secondary"></i>
           </a>
-          <a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${inv.id},'${escape_html(inv.invoice_number)}')">
-            <i class="ti ti-trash fs-5"></i>
-          </a>
+          ${can_delete ? `<a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${inv.id},'${escape_html(inv.invoice_number)}')"><i class="ti ti-trash fs-5"></i></a>` : ''}
         </td>
       </tr>`;
     });
@@ -410,9 +409,7 @@
           <a href="javascript:;" title="View GL Entry" class="me-2" onclick="show_gl_modal('credit_note',${cn.id})">
             <i class="ti ti-book fs-5 text-secondary"></i>
           </a>
-          <a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${cn.id},'${escape_html(cn.invoice_number)}')">
-            <i class="ti ti-trash fs-5"></i>
-          </a>
+          ${can_delete ? `<a href="javascript:;" title="Delete" class="link-danger" onclick="delete_invoice(${cn.id},'${escape_html(cn.invoice_number)}')"><i class="ti ti-trash fs-5"></i></a>` : ''}
         </td>
       </tr>`;
     });
diff --git a/app/setting/api/engine/change_password.php b/app/setting/api/engine/change_password.php
index c554172..363dea0 100644
--- a/app/setting/api/engine/change_password.php
+++ b/app/setting/api/engine/change_password.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/PasswordManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/PasswordManager.php';
 
     $pm = new PasswordManager($pdo1, $include_url);
     $pm->handleChange($user_id, $data);
\ No newline at end of file
diff --git a/app/setting/api/engine/company_setting.php b/app/setting/api/engine/company_setting.php
index 5970d2d..93be509 100644
--- a/app/setting/api/engine/company_setting.php
+++ b/app/setting/api/engine/company_setting.php
@@ -1,6 +1,6 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_once '../../../assets/utils/classes/CompanySettingManager.php';
 
 if (($data['action'] ?? '') === 'update') {
diff --git a/app/setting/api/engine/gl_maintenance.php b/app/setting/api/engine/gl_maintenance.php
index 38805ef..ec1dfb2 100644
--- a/app/setting/api/engine/gl_maintenance.php
+++ b/app/setting/api/engine/gl_maintenance.php
@@ -1,6 +1,6 @@
 <?php
 session_start();
-require '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/db_auth.php';
 require_role($user_role, ['owner', 'admin']);
 require_once '../../../assets/utils/classes_ac/EtlManager.php';
 
diff --git a/app/setting/api/engine/manage_company.php b/app/setting/api/engine/manage_company.php
index e20f40e..678d041 100644
--- a/app/setting/api/engine/manage_company.php
+++ b/app/setting/api/engine/manage_company.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/CompanyProfileManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/CompanyProfileManager.php';
 
     if ($user_role !== 'owner') { http_response_code(403); exit(json_encode(['success' => 0, 'message' => 'Only the owner can modify this setting.'])); }
 
diff --git a/app/setting/api/engine/manage_profile.php b/app/setting/api/engine/manage_profile.php
index 182fda7..094b761 100644
--- a/app/setting/api/engine/manage_profile.php
+++ b/app/setting/api/engine/manage_profile.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/FileUploader.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/FileUploader.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     try {
         $um = new UserManager($pdo1, $company_id, $user_id);
diff --git a/app/setting/api/engine/manage_smtp.php b/app/setting/api/engine/manage_smtp.php
index 5354b3a..1dbabb0 100644
--- a/app/setting/api/engine/manage_smtp.php
+++ b/app/setting/api/engine/manage_smtp.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/SmtpManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/SmtpManager.php';
 
     if ($user_role !== 'owner') { http_response_code(403); exit(json_encode(['success' => 0, 'message' => 'Only the owner can modify this setting.'])); }
 
diff --git a/app/setting/api/engine/manage_users.php b/app/setting/api/engine/manage_users.php
index a98213c..2683f11 100644
--- a/app/setting/api/engine/manage_users.php
+++ b/app/setting/api/engine/manage_users.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     if ($user_role !== 'owner') { http_response_code(403); exit(json_encode(['success' => 0, 'message' => 'Only the owner can modify this setting.'])); }
 
diff --git a/app/setting/api/engine/request_reset_otp.php b/app/setting/api/engine/request_reset_otp.php
index 2f61a28..986e885 100644
--- a/app/setting/api/engine/request_reset_otp.php
+++ b/app/setting/api/engine/request_reset_otp.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
     define('UNAUTHENTICATED_ROUTE', true);
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/PasswordResetManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/PasswordResetManager.php';
 
     $prm = new PasswordResetManager($pdo1, $pdo2, $include_url, $SMTP, $pinkey);
     $prm->handleRequestOtp($user_id, $company_id);
\ No newline at end of file
diff --git a/app/setting/api/engine/reset_password_otp.php b/app/setting/api/engine/reset_password_otp.php
index 1c169ae..d4daa40 100644
--- a/app/setting/api/engine/reset_password_otp.php
+++ b/app/setting/api/engine/reset_password_otp.php
@@ -1,8 +1,8 @@
 <?php
     session_start();
     define('UNAUTHENTICATED_ROUTE', true);
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/PasswordResetManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/PasswordResetManager.php';
 
     $prm = new PasswordResetManager($pdo1, $pdo2, $include_url, $SMTP, $pinkey);
     $prm->handleConfirmReset($user_id, $data);
\ No newline at end of file
diff --git a/app/setting/api/engine/retrieve_company.php b/app/setting/api/engine/retrieve_company.php
index 232f421..2b0e3cd 100644
--- a/app/setting/api/engine/retrieve_company.php
+++ b/app/setting/api/engine/retrieve_company.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/CompanyProfileManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/CompanyProfileManager.php';
 
     try {
         $company_profile = new CompanyProfileManager($pdo1, $company_id);
diff --git a/app/setting/api/engine/retrieve_profile.php b/app/setting/api/engine/retrieve_profile.php
index e1ce411..6464f4e 100644
--- a/app/setting/api/engine/retrieve_profile.php
+++ b/app/setting/api/engine/retrieve_profile.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     $um = new UserManager($pdo1, $company_id, $user_id);
 
diff --git a/app/setting/api/engine/retrieve_smtp.php b/app/setting/api/engine/retrieve_smtp.php
index 82292cc..db09c0c 100644
--- a/app/setting/api/engine/retrieve_smtp.php
+++ b/app/setting/api/engine/retrieve_smtp.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/SmtpManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/SmtpManager.php';
 
     try {
         $smtp = new SmtpManager($pdo1, $company_id, $method, $pinkey, $iv);
diff --git a/app/setting/api/engine/retrieve_users.php b/app/setting/api/engine/retrieve_users.php
index d6fdf55..aaf86a6 100644
--- a/app/setting/api/engine/retrieve_users.php
+++ b/app/setting/api/engine/retrieve_users.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     $um = new UserManager($pdo1, $company_id, $user_id);
 
diff --git a/app/setting/api/engine/search_users.php b/app/setting/api/engine/search_users.php
index c446091..44ff051 100644
--- a/app/setting/api/engine/search_users.php
+++ b/app/setting/api/engine/search_users.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/UserManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/UserManager.php';
 
     $keyword = trim($data['keyword'] ?? '');
     $um      = new UserManager($pdo1, $company_id, $user_id);
diff --git a/app/setting/api/engine/switch_branch.php b/app/setting/api/engine/switch_branch.php
index f145b6a..4f84cb9 100644
--- a/app/setting/api/engine/switch_branch.php
+++ b/app/setting/api/engine/switch_branch.php
@@ -6,8 +6,8 @@
  * action: 'update' → switch to the requested company_id
  */
 session_start();
-require '../../../assets/utils/db_auth.php';
-require '../../../assets/utils/classes/UserManager.php';
+require_once '../../../assets/utils/db_auth.php';
+require_once '../../../assets/utils/classes/UserManager.php';
 
 $action = $data['action'] ?? '';
 $um = new UserManager($pdo1, $company_id, $user_id);
diff --git a/app/setting/api/engine/test_smtp.php b/app/setting/api/engine/test_smtp.php
index 772ef86..6c3d926 100644
--- a/app/setting/api/engine/test_smtp.php
+++ b/app/setting/api/engine/test_smtp.php
@@ -1,7 +1,7 @@
 <?php
     session_start();
-    require '../../../assets/utils/db_auth.php';
-    require '../../../assets/utils/classes/SmtpManager.php';
+    require_once '../../../assets/utils/db_auth.php';
+    require_once '../../../assets/utils/classes/SmtpManager.php';
 
     if ($user_role !== 'owner') { http_response_code(403); exit(json_encode(['success' => 0, 'message' => 'Only the owner can modify this setting.'])); }