Complete WooCommerce Plugin Development Guide: From Concept to Deployment

<?php
/**
 * Plugin Name: My WooCommerce Plugin
 * Plugin URI: https://example.com
 * Description: Custom WooCommerce plugin for XYZ functionality.
 * Version: 1.0.0
 * Author: MAMEDUL ISLAM
 * Author URI: https://example.com
 * Text Domain: my-woocommerce-plugin
 * Domain Path: /languages
 */

if ( ! defined( 'ABSPATH' ) ) {
    exit; // Exit if accessed directly
}

// Define constants
define('MWP_PLUGIN_DIR', plugin_dir_path(__FILE__));
define('MWP_PLUGIN_URL', plugin_dir_url(__FILE__));
define('MWP_VERSION', '1.0.0');

// Include dependencies
require_once MWP_PLUGIN_DIR . 'includes/functions.php';
require_once MWP_PLUGIN_DIR . 'includes/class-admin-settings.php';
require_once MWP_PLUGIN_DIR . 'includes/class-cron-jobs.php';
require_once MWP_PLUGIN_DIR . 'includes/class-api-integration.php';

// Initialize plugin
add_action('plugins_loaded', 'mwp_init_plugin');
function mwp_init_plugin() {
    if ( class_exists('WooCommerce') ) {
        MWP_Admin_Settings::init();
        MWP_Cron_Jobs::init();
        MWP_API_Integration::init();
    }
}

<?php
class MWP_Admin_Settings {

    public static function init() {
        add_action('admin_menu', [__CLASS__, 'add_menu']);
        add_action('admin_init', [__CLASS__, 'register_settings']);
    }

    public static function add_menu() {
        add_submenu_page(
            'woocommerce',
            'My Plugin Settings',
            'My Plugin',
            'manage_options',
            'mwp-settings',
            [__CLASS__, 'settings_page_html']
        );
    }

    public static function register_settings() {
        register_setting('mwp_settings_group', 'mwp_api_key');
        register_setting('mwp_settings_group', 'mwp_option_enable');
    }

    public static function settings_page_html() {
        ?>
        <div class="wrap">
            <h1>My Plugin Settings</h1>
            <form method="post" action="options.php">
                <?php settings_fields('mwp_settings_group'); ?>
                <?php do_settings_sections('mwp_settings_group'); ?>
                <table class="form-table">
                    <tr>
                        <th scope="row">API Key</th>
                        <td><input type="text" name="mwp_api_key" value="<?php echo esc_attr(get_option('mwp_api_key')); ?>" class="regular-text"></td>
                    </tr>
                    <tr>
                        <th scope="row">Enable Feature</th>
                        <td><input type="checkbox" name="mwp_option_enable" value="yes" <?php checked(get_option('mwp_option_enable'), 'yes'); ?>></td>
                    </tr>
                </table>
                <?php submit_button(); ?>
            </form>
        </div>
        <?php
    }
}

add_action('woocommerce_after_order_notes', 'mwp_custom_checkout_field');
function mwp_custom_checkout_field($checkout) {
    echo '<div id="mwp_custom_field"><h2>Custom Info</h2>';
    woocommerce_form_field('mwp_field', array(
        'type' => 'text',
        'class' => array('mwp-field form-row-wide'),
        'label' => __('Enter something'),
        'required' => true,
    ), $checkout->get_value('mwp_field'));
    echo '</div>';
}

add_action('woocommerce_checkout_update_order_meta', 'mwp_save_custom_field');
function mwp_save_custom_field($order_id) {
    if (!empty($_POST['mwp_field'])) {
        update_post_meta($order_id, 'mwp_field', sanitize_text_field($_POST['mwp_field']));
    }
}

class MWP_API_Integration {

    public static function init() {
        add_action('init', [__CLASS__, 'fetch_data']);
    }

    public static function fetch_data() {
        $api_url = 'https://api.example.com/orders';
        $response = wp_remote_get($api_url, [
            'headers' => [
                'Authorization' => 'Bearer ' . get_option('mwp_api_key')
            ]
        ]);

        if (is_wp_error($response)) return;

        $data = json_decode(wp_remote_retrieve_body($response), true);

        foreach ($data as $order) {
            // Create WooCommerce orders programmatically
            $new_order = wc_create_order();
            $new_order->add_product(wc_get_product($order['product_id']), $order['quantity']);
            $new_order->set_address($order['billing'], 'billing');
            $new_order->calculate_totals();
        }
    }
}

class MWP_Cron_Jobs {

    public static function init() {
        add_action('mwp_hourly_event', [__CLASS__, 'run_task']);
        if (!wp_next_scheduled('mwp_hourly_event')) {
            wp_schedule_event(time(), 'hourly', 'mwp_hourly_event');
        }
    }

    public static function run_task() {
        // e.g., Sync orders or send emails
    }

    public static function deactivate() {
        $timestamp = wp_next_scheduled('mwp_hourly_event');
        wp_unschedule_event($timestamp, 'mwp_hourly_event');
    }
}

// On plugin deactivation
register_deactivation_hook(__FILE__, ['MWP_Cron_Jobs', 'deactivate']);

// Adding meta to product
update_post_meta($product_id, '_custom_meta_key', 'value');

// Retrieving meta
$value = get_post_meta($product_id, '_custom_meta_key', true);

// Extend WC_Email
class WC_Email_Custom_Notification extends WC_Email {
    public function __construct() {
        $this->id = 'custom_notification';
        $this->title = 'Custom Notification';
        $this->description = 'Send a custom email to customer';
        $this->template_html = 'emails/custom-email.php';
        parent::__construct();
    }

    public function trigger($order_id) {
        $this->object = wc_get_order($order_id);
        $this->recipient = $this->object->get_billing_email();
        if (!$this->is_enabled() || !$this->get_recipient()) return;
        $this->send($this->get_recipient(), $this->get_subject(), $this->get_content(), $this->get_headers(), $this->get_attachments());
    }
}