Release version 1.1.18 - Fix root cause of duplicate settings

Identified and fixed the actual root cause of duplicate settings page:
automatic instantiation in settings file being executed multiple times.

Root Cause Analysis:
- Settings file ended with: return new WC_TPP_Settings();
- File is in Composer's classmap for autoloading
- When autoloader loads class, it executes the entire file including instantiation
- Each include/autoload created a NEW instance despite admin singleton pattern
- Admin singleton prevented multiple admin instances but not multiple settings instances

The Fix:
- Removed automatic instantiation (return new) from settings file
- Settings file now only contains class definition
- Admin class explicitly creates instance: new WC_TPP_Settings()
- Changed from include to require_once to prevent multiple file loads
- Settings instance now created exactly once, when filter needs it

Fixes:
- Settings page rendering twice in WooCommerce backend
- Multiple WC_TPP_Settings instances being created
- Composer autoload triggering unintended instantiation

Changes:
- Removed line 145 from class-wc-tpp-settings.php (return new WC_TPP_Settings())
- Modified add_settings_page() to use require_once + explicit new
- Settings file now side-effect free, safe for autoloading

Technical Details:
- Composer classmap autoloader includes files when class is referenced
- Previous code had side effect (instantiation) on every include
- New code separates class definition from instantiation
- Instance creation now controlled explicitly by admin class
- require_once ensures file loaded once even if accessed multiple times

Updated Files:
- includes/class-wc-tpp-settings.php (removed return new line)
- includes/class-wc-tpp-admin.php (explicit instantiation)
- wc-tier-and-package-prices.php (version 1.1.18)
- composer.json (version 1.1.18)
- CHANGELOG.md (v1.1.18 section)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitignore

@@ -21,6 +21,7 @@ npm-debug.log
 
 # Logs
 *.log
+/logs
 
 # Notes
 notes.*

CHANGELOG.md

@@ -5,6 +5,194 @@ All notable changes to WooCommerce Tier and Package Prices will be documented in
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.1.18] - 2025-12-22
+
+### Fixed
+
+- **ROOT CAUSE IDENTIFIED**: Settings page rendering twice due to automatic instantiation in settings file
+- Settings file being included multiple times via Composer autoloader creating duplicate instances
+
+### Changed
+
+- Removed `return new WC_TPP_Settings();` from bottom of settings file
+- Changed admin class to explicitly instantiate settings with `new WC_TPP_Settings()`
+- Changed from `include` to `require_once` for settings file to prevent multiple loads
+
+### Technical Details
+
+- Settings file (class-wc-tpp-settings.php) was creating instance automatically on include
+- File is in Composer's classmap, so when autoloaded it executed instantiation again
+- Each include/autoload created new instance even with singleton pattern in admin class
+- Solution: Remove automatic instantiation, use `require_once` + explicit `new` in admin class
+- Now settings instance only created once, explicitly, when needed by filter
+- Composer autoload can load class definition without side effects
+
+## [1.1.17] - 2025-12-22
+
+### Fixed
+
+- Settings page still rendering twice despite singleton pattern in v1.1.16
+- Filter adding settings instance to array multiple times when called repeatedly
+
+### Changed
+
+- Added duplicate detection in `add_settings_page()` filter method
+- Filter now checks if settings instance already exists in array before adding
+
+### Technical Details
+
+- Added foreach loop to check existing settings pages in array
+- Uses strict comparison (`===`) to detect if exact instance already present
+- Returns early if settings instance found, preventing duplicate array entries
+- Complements singleton pattern from v1.1.16 with array-level duplicate prevention
+- Handles edge case where WooCommerce calls filter multiple times
+
+## [1.1.16] - 2025-12-22
+
+### Fixed
+
+- Settings page still rendering twice in WooCommerce backend despite v1.1.15 fix
+- Multiple instantiation of WC_TPP_Admin and WC_TPP_Settings classes
+
+### Changed
+
+- Implemented singleton pattern for WC_TPP_Admin class with `get_instance()` method
+- Made WC_TPP_Admin constructor private to prevent direct instantiation
+- Added static caching of WC_TPP_Settings instance to prevent duplicate creation
+- Changed class instantiation from `new WC_TPP_Admin()` to `WC_TPP_Admin::get_instance()`
+
+### Technical Details
+
+- Added `private static $instance` property to WC_TPP_Admin class
+- Added `private static $settings_instance` property to cache settings page instance
+- Modified `add_settings_page()` to check and reuse cached settings instance
+- Ensures only one instance of each class exists throughout plugin lifecycle
+- Prevents duplicate filter registrations even if called multiple times
+
+## [1.1.15] - 2025-12-22
+
+### Fixed
+
+- Settings page rendering twice in WooCommerce settings
+- Duplicate instantiation of WC_TPP_Settings class causing double rendering
+
+### Technical Details
+
+- Removed conditional `if (class_exists('WC_TPP_Settings'))` wrapper from settings return statement
+- Settings class now only instantiated via `return new WC_TPP_Settings();` when included by admin class
+- Matches v1.1.2 pattern where settings file returns instance without automatic instantiation
+- Prevents double registration in WooCommerce settings pages array
+
+## [1.1.14] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Plugin completely non-functional in v1.1.8-1.1.13 - no settings, no frontend, no backend
+- Classes never instantiated due to incorrect initialization pattern introduced in v1.1.8
+- Restored v1.1.2 pattern: classes auto-instantiate when files are included
+- All plugin functionality now working: settings page, product meta boxes, frontend display, cart integration
+
+### Changed
+
+- Reverted to direct class instantiation pattern from v1.1.2 (last known working version)
+- Removed `init_classes()` method and `woocommerce_loaded` hook approach from v1.1.8
+- Each class file now instantiates itself with `new ClassName()` at end of file
+- Simplified plugin initialization for better reliability
+
+### Technical Details
+
+- Restored class instantiation in all 5 component files:
+  - `class-wc-tpp-admin.php`: Added `new WC_TPP_Admin();` after class declaration
+  - `class-wc-tpp-product-meta.php`: Added `new WC_TPP_Product_Meta();` after class declaration
+  - `class-wc-tpp-frontend.php`: Added `new WC_TPP_Frontend();` after class declaration
+  - `class-wc-tpp-cart.php`: Added `new WC_TPP_Cart();` after class declaration
+  - `class-wc-tpp-settings.php`: Already has instantiation via return statement
+- Removed `init_classes()` method from main plugin class
+- Removed `woocommerce_loaded` hook that delayed class instantiation
+- Classes now instantiate immediately when `require_once` loads them
+- All `class_exists()` guards remain in place for redeclaration protection
+
+## [1.1.13] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Class redeclaration errors for all plugin component classes affecting version 1.1.12
+- Fatal errors "Cannot redeclare class WC_TPP_Admin", "Cannot redeclare class WC_TPP_Product_Meta", "Cannot redeclare class WC_TPP_Frontend", "Cannot redeclare class WC_TPP_Cart", "Cannot redeclare class WC_TPP_Settings"
+- Plugin functionality completely broken in v1.1.12 - no settings page, no frontend display, no backend controls
+- All plugin features now working correctly after adding class guards
+
+### Technical Details
+
+- Wrapped all 5 plugin component class declarations in `class_exists()` checks:
+  - `WC_TPP_Admin` (includes/class-wc-tpp-admin.php)
+  - `WC_TPP_Product_Meta` (includes/class-wc-tpp-product-meta.php)
+  - `WC_TPP_Frontend` (includes/class-wc-tpp-frontend.php)
+  - `WC_TPP_Cart` (includes/class-wc-tpp-cart.php)
+  - `WC_TPP_Settings` (includes/class-wc-tpp-settings.php)
+- Completes comprehensive redeclaration protection started in v1.1.9-1.1.12
+- All functions, constants, and classes now fully protected against redeclaration
+- Plugin now activates and functions correctly without fatal errors
+
+## [1.1.12] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Class redeclaration error for `WC_Tier_Package_Prices` affecting version 1.1.11
+- Fatal error "Cannot redeclare class WC_Tier_Package_Prices" when plugin file loaded multiple times
+- Plugin activation failures caused by class redeclaration
+
+### Technical Details
+
+- Wrapped `WC_Tier_Package_Prices` class declaration in `class_exists()` check
+- Completes comprehensive redeclaration protection for all plugin components
+- Prevents fatal errors during WordPress plugin activation/deactivation cycles
+- All functions, constants, and classes now safely guarded against redeclaration
+
+## [1.1.11] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Constant redeclaration warnings/errors for plugin constants affecting versions 1.1.3-1.1.10
+- Potential errors when plugin constants (WC_TPP_VERSION, WC_TPP_PLUGIN_DIR, etc.) already defined
+- Plugin initialization failures caused by constant redeclaration
+
+### Technical Details
+
+- Wrapped all `define()` calls in `defined()` checks for WC_TPP_VERSION, WC_TPP_PLUGIN_DIR, WC_TPP_PLUGIN_URL, WC_TPP_PLUGIN_BASENAME
+- Prevents warnings/errors during WordPress plugin activation/deactivation cycles
+- Completes comprehensive protection against all redeclaration issues
+- All global functions and constants now safely guarded
+
+## [1.1.10] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Function redeclaration error for `wc_tpp_init()` affecting version 1.1.9
+- Fatal error "Cannot redeclare function wc_tpp_init()" when plugin file loaded multiple times
+- Plugin activation failures caused by function redeclaration
+
+### Technical Details
+
+- Wrapped `wc_tpp_init()` function in `function_exists()` check
+- Completes the fix started in v1.1.9 by protecting all global functions
+- Prevents fatal errors during WordPress plugin activation cycles
+- Both `wc_tpp_woocommerce_missing_notice()` and `wc_tpp_init()` now safely guarded
+
+## [1.1.9] - 2025-12-22
+
+### Fixed
+
+- **CRITICAL:** Function redeclaration error for `wc_tpp_woocommerce_missing_notice()` affecting versions 1.1.3-1.1.8
+- Fatal error "Cannot redeclare function wc_tpp_woocommerce_missing_notice()" when plugin file loaded multiple times
+- Plugin activation and deactivation failures caused by function redeclaration
+
+### Technical Details
+
+- Wrapped `wc_tpp_woocommerce_missing_notice()` function in `function_exists()` check
+- Prevents fatal error during WordPress plugin activation/deactivation cycles
+- Ensures function can safely be declared even if file is included multiple times
+- Moved function declaration before WooCommerce check for better code organization
+
 ## [1.1.8] - 2025-12-22
 
 ### Fixed

composer.json

@@ -1,7 +1,7 @@
 {
     "name": "magdev/wc-tier-package-prices",
     "description": "WooCommerce plugin for tier pricing and package prices with Twig templates",
-    "version": "1.1.8",
+    "version": "1.1.18",
     "type": "wordpress-plugin",
     "license": "GPL-2.0-or-later",
     "authors": [

includes/class-wc-tpp-admin.php

@@ -7,9 +7,20 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-class WC_TPP_Admin {
+if (!class_exists('WC_TPP_Admin')) {
+    class WC_TPP_Admin {
 
-    public function __construct() {
+    private static $instance = null;
+    private static $settings_instance = null;
+
+    public static function get_instance() {
+        if (null === self::$instance) {
+            self::$instance = new self();
+        }
+        return self::$instance;
+    }
+
+    private function __construct() {
         add_filter('woocommerce_get_settings_pages', array($this, 'add_settings_page'));
         add_action('admin_enqueue_scripts', array($this, 'enqueue_admin_scripts'));
     }
@@ -18,7 +29,19 @@ class WC_TPP_Admin {
      * Add settings page to WooCommerce settings
      */
     public function add_settings_page($settings) {
-        $settings[] = include WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-settings.php';
+        if (null === self::$settings_instance) {
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-settings.php';
+            self::$settings_instance = new WC_TPP_Settings();
+        }
+
+        // Check if our settings page is already in the array to prevent duplicates
+        foreach ($settings as $settings_page) {
+            if ($settings_page === self::$settings_instance) {
+                return $settings;
+            }
+        }
+
+        $settings[] = self::$settings_instance;
         return $settings;
     }
 
@@ -29,3 +52,6 @@ class WC_TPP_Admin {
         }
     }
 }
+
+WC_TPP_Admin::get_instance();
+}

includes/class-wc-tpp-cart.php

@@ -7,7 +7,8 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-class WC_TPP_Cart {
+if (!class_exists('WC_TPP_Cart')) {
+    class WC_TPP_Cart {
 
     public function __construct() {
         add_action('woocommerce_before_calculate_totals', array($this, 'apply_tier_package_pricing'), 10, 1);
@@ -247,3 +248,6 @@ class WC_TPP_Cart {
         return $editable;
     }
 }
+
+new WC_TPP_Cart();
+}

includes/class-wc-tpp-frontend.php

@@ -7,7 +7,8 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-class WC_TPP_Frontend {
+if (!class_exists('WC_TPP_Frontend')) {
+    class WC_TPP_Frontend {
 
     public function __construct() {
         add_action('wp_enqueue_scripts', array($this, 'enqueue_scripts'));
@@ -182,3 +183,6 @@ class WC_TPP_Frontend {
         return $new_html;
     }
 }
+
+new WC_TPP_Frontend();
+}

includes/class-wc-tpp-product-meta.php

@@ -7,7 +7,8 @@ if (!defined('ABSPATH')) {
     exit;
 }
 
-class WC_TPP_Product_Meta {
+if (!class_exists('WC_TPP_Product_Meta')) {
+    class WC_TPP_Product_Meta {
 
     public function __construct() {
         add_action('woocommerce_product_options_pricing', array($this, 'add_tier_pricing_fields'));
@@ -167,3 +168,6 @@ class WC_TPP_Product_Meta {
         update_post_meta($post_id, '_wc_tpp_restrict_to_packages', $restrict_to_packages);
     }
 }
+
+new WC_TPP_Product_Meta();
+}

includes/class-wc-tpp-settings.php

@@ -18,7 +18,8 @@ if (!class_exists('WC_Settings_Page')) {
 /**
  * WC_TPP_Settings class
  */
-class WC_TPP_Settings extends WC_Settings_Page {
+if (!class_exists('WC_TPP_Settings')) {
+    class WC_TPP_Settings extends WC_Settings_Page {
 
     /**
      * Constructor
@@ -139,5 +140,4 @@ class WC_TPP_Settings extends WC_Settings_Page {
         WC_Admin_Settings::save_fields($settings);
     }
 }
-
+}
-return new WC_TPP_Settings();

releases/wc-tier-and-package-prices-1.1.10.zip.md5

@@ -0,0 +1 @@
+81be5283219cfa722f6d382a788e7dc1  releases/wc-tier-and-package-prices-1.1.10.zip

releases/wc-tier-and-package-prices-1.1.10.zip.sha256

@@ -0,0 +1 @@
+2d3b01e61c8a03a8f20bc99b2019ca50fa08ecd68188feb2d2105dfe35d36f0d  releases/wc-tier-and-package-prices-1.1.10.zip

releases/wc-tier-and-package-prices-1.1.11.zip.md5

@@ -0,0 +1 @@
+4a0c0b07b29d4b7046f9d3ff3f091321  releases/wc-tier-and-package-prices-1.1.11.zip

releases/wc-tier-and-package-prices-1.1.11.zip.sha256

@@ -0,0 +1 @@
+3da9423d136a2ff254b61577ba1f84d4c0f0d1e57bae361ac29c90327feeeceb  releases/wc-tier-and-package-prices-1.1.11.zip

releases/wc-tier-and-package-prices-1.1.12.zip.md5

@@ -0,0 +1 @@
+c1c0b5880636686227246be2c37dc42a  releases/wc-tier-and-package-prices-1.1.12.zip

releases/wc-tier-and-package-prices-1.1.12.zip.sha256

@@ -0,0 +1 @@
+05b32356d46803dbb7fa17c13a2d8da96f77126746e2895e2f5c6dd0e7b490ff  releases/wc-tier-and-package-prices-1.1.12.zip

releases/wc-tier-and-package-prices-1.1.13.zip.md5

@@ -0,0 +1 @@
+8572eed399554905fbf331d18f0677a0  wc-tier-and-package-prices-1.1.13.zip

releases/wc-tier-and-package-prices-1.1.13.zip.sha256

@@ -0,0 +1 @@
+83e29b2e40dd43e77bd83cd03d4ccc54ef53555b55544eba4d38161101f79f20  wc-tier-and-package-prices-1.1.13.zip

releases/wc-tier-and-package-prices-1.1.14.zip.md5

@@ -0,0 +1 @@
+e0cc51d1493ed35ab254220d9f46997b  wc-tier-and-package-prices-1.1.14.zip

releases/wc-tier-and-package-prices-1.1.14.zip.sha256

@@ -0,0 +1 @@
+8a2ce7438ee49baffdcaaf323b6426d73dd1cf704bea94a80fcce27a42c097ad  wc-tier-and-package-prices-1.1.14.zip

releases/wc-tier-and-package-prices-1.1.8.zip.md5

@@ -0,0 +1 @@
+666e1acad9f349982463b65d0e3e7fa3  wc-tier-and-package-prices-1.1.8.zip

releases/wc-tier-and-package-prices-1.1.8.zip.sha256

@@ -0,0 +1 @@
+2c100d0d100a6fd7bd8f9c9b154d878a675bc795c5fddb19314bc9991b9a60ba  wc-tier-and-package-prices-1.1.8.zip

releases/wc-tier-and-package-prices-1.1.9.zip.md5

@@ -0,0 +1 @@
+7421aceb8d1cc89b7d15b19d68cdfabe  wc-tier-and-package-prices-1.1.9.zip

releases/wc-tier-and-package-prices-1.1.9.zip.sha256

@@ -0,0 +1 @@
+8224bf8b9bfc3dc760d77c61700d27c31db1a67b70834d8b6a4581df66fd45bd  wc-tier-and-package-prices-1.1.9.zip

wc-tier-and-package-prices.php

@@ -4,7 +4,7 @@
  * Plugin Name: WooCommerce Tier and Package Prices
  * Plugin URI: https://src.bundespruefstelle.ch/magdev/wc-tier-package-prices
  * Description: Add tier pricing and package prices to WooCommerce products with configurable quantities at fixed prices
- * Version: 1.1.8
+ * Version: 1.1.18
  * Author: Marco Graetsch
  * Author URI: https://src.bundespruefstelle.ch/magdev
  * Text Domain: wc-tier-package-prices
@@ -22,14 +22,35 @@ if (!defined('ABSPATH')) {
 }
 
 // Define plugin constants
-define('WC_TPP_VERSION', '1.1.8');
+if (!defined('WC_TPP_VERSION')) {
-define('WC_TPP_PLUGIN_DIR', plugin_dir_path(__FILE__));
+    define('WC_TPP_VERSION', '1.1.18');
-define('WC_TPP_PLUGIN_URL', plugin_dir_url(__FILE__));
+}
-define('WC_TPP_PLUGIN_BASENAME', plugin_basename(__FILE__));
+if (!defined('WC_TPP_PLUGIN_DIR')) {
+    define('WC_TPP_PLUGIN_DIR', plugin_dir_path(__FILE__));
+}
+if (!defined('WC_TPP_PLUGIN_URL')) {
+    define('WC_TPP_PLUGIN_URL', plugin_dir_url(__FILE__));
+}
+if (!defined('WC_TPP_PLUGIN_BASENAME')) {
+    define('WC_TPP_PLUGIN_BASENAME', plugin_basename(__FILE__));
+}
 
 // Load Composer autoloader
 require_once WC_TPP_PLUGIN_DIR . 'vendor/autoload.php';
 
+/**
+ * Display WooCommerce missing notice
+ */
+if (!function_exists('wc_tpp_woocommerce_missing_notice')) {
+    function wc_tpp_woocommerce_missing_notice() {
+        ?>
+        <div class="notice notice-error">
+            <p><?php _e('WooCommerce Tier and Package Prices requires WooCommerce to be installed and active.', 'wc-tier-package-prices'); ?></p>
+        </div>
+        <?php
+    }
+}
+
 /**
  * Check if WooCommerce is active
  */
@@ -38,84 +59,70 @@ if (!in_array('woocommerce/woocommerce.php', apply_filters('active_plugins', get
     return;
 }
 
-function wc_tpp_woocommerce_missing_notice() {
-    ?>
-    <div class="notice notice-error">
-        <p><?php _e('WooCommerce Tier and Package Prices requires WooCommerce to be installed and active.', 'wc-tier-package-prices'); ?></p>
-    </div>
-    <?php
-}
-
 /**
  * Main plugin class
  */
-class WC_Tier_Package_Prices {
+if (!class_exists('WC_Tier_Package_Prices')) {
+    class WC_Tier_Package_Prices {
 
-    private static $instance = null;
+        private static $instance = null;
 
-    public static function get_instance() {
+        public static function get_instance() {
-        if (null === self::$instance) {
+            if (null === self::$instance) {
-            self::$instance = new self();
+                self::$instance = new self();
+            }
+            return self::$instance;
         }
-        return self::$instance;
-    }
 
-    private function __construct() {
+        private function __construct() {
-        $this->init_hooks();
+            $this->init_hooks();
-        $this->includes();
+            $this->includes();
-    }
-
-    private function init_hooks() {
-        add_action('plugins_loaded', array($this, 'load_textdomain'));
-        add_action('before_woocommerce_init', array($this, 'declare_hpos_compatibility'));
-        register_activation_hook(__FILE__, array($this, 'activate'));
-        register_deactivation_hook(__FILE__, array($this, 'deactivate'));
-    }
-
-    private function includes() {
-        require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-template-loader.php';
-        require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-admin.php';
-        require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-product-meta.php';
-        require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-frontend.php';
-        require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-cart.php';
-
-        // Instantiate classes after WooCommerce is loaded
-        add_action('woocommerce_loaded', array($this, 'init_classes'));
-    }
-
-    public function init_classes() {
-        new WC_TPP_Admin();
-        new WC_TPP_Product_Meta();
-        new WC_TPP_Frontend();
-        new WC_TPP_Cart();
-    }
-
-    public function declare_hpos_compatibility() {
-        if (class_exists(\Automattic\WooCommerce\Utilities\FeaturesUtil::class)) {
-            \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility('custom_order_tables', __FILE__, true);
         }
-    }
 
-    public function load_textdomain() {
+        private function init_hooks() {
-        load_plugin_textdomain('wc-tier-package-prices', false, dirname(WC_TPP_PLUGIN_BASENAME) . '/languages');
+            add_action('plugins_loaded', array($this, 'load_textdomain'));
-    }
+            add_action('before_woocommerce_init', array($this, 'declare_hpos_compatibility'));
+            register_activation_hook(__FILE__, array($this, 'activate'));
+            register_deactivation_hook(__FILE__, array($this, 'deactivate'));
+        }
 
-    public function activate() {
+        private function includes() {
-        // Add default options
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-template-loader.php';
-        add_option('wc_tpp_enable_tier_pricing', 'yes');
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-admin.php';
-        add_option('wc_tpp_enable_package_pricing', 'yes');
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-product-meta.php';
-        add_option('wc_tpp_display_table', 'yes');
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-frontend.php';
-        flush_rewrite_rules();
+            require_once WC_TPP_PLUGIN_DIR . 'includes/class-wc-tpp-cart.php';
-    }
+        }
 
-    public function deactivate() {
+        public function declare_hpos_compatibility() {
-        flush_rewrite_rules();
+            if (class_exists(\Automattic\WooCommerce\Utilities\FeaturesUtil::class)) {
+                \Automattic\WooCommerce\Utilities\FeaturesUtil::declare_compatibility('custom_order_tables', __FILE__, true);
+            }
+        }
+
+        public function load_textdomain() {
+            load_plugin_textdomain('wc-tier-package-prices', false, dirname(WC_TPP_PLUGIN_BASENAME) . '/languages');
+        }
+
+        public function activate() {
+            // Add default options
+            add_option('wc_tpp_enable_tier_pricing', 'yes');
+            add_option('wc_tpp_enable_package_pricing', 'yes');
+            add_option('wc_tpp_display_table', 'yes');
+            flush_rewrite_rules();
+        }
+
+        public function deactivate() {
+            flush_rewrite_rules();
+        }
     }
 }
 
 // Initialize the plugin
-function wc_tpp_init() {
+if (!function_exists('wc_tpp_init')) {
-    return WC_Tier_Package_Prices::get_instance();
+    function wc_tpp_init() {
+        return WC_Tier_Package_Prices::get_instance();
+    }
 }
 
 add_action('plugins_loaded', 'wc_tpp_init', 11);