Extending WooCommerce COD payment gateway in a plugin - php

Question

I would like to understand the sequence various classes are loaded in Wordpress.
There are many plugins available in Wordpress, then who will be loaded earlier than another.
Consider I would like to develop a plugin that will use some existing class of Woocommerce. Basically my custom plugin will extend some class of Woocommerce (for example : WC_Gateway_COD)
How I can ensure the existing class ‘WC_Gateway_COD’ is already defined & loaded before it execute the below statement ?
if (class_exists('WC_Gateway_COD')) {
class WC_my_custom_class extends WC_Gateway_COD {
…..
….
}
}

Answer 1

To make a custom gateway based on an existing WooCommerce payment method as COD, It's recommended to copy the source code from WC_Gateway_COD Class in a plugin (adapting the code for your needs) like:
defined( 'ABSPATH' ) or exit;
// Make sure WooCommerce is active
if ( ! in_array( 'woocommerce/woocommerce.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ) ) ) {
return;
}
add_filter( 'woocommerce_payment_gateways', 'wc_custom_add_to_gateways' );
function wc_custom_add_to_gateways( $gateways ) {
$gateways[] = 'WC_Gateway_COD2';
return $gateways;
}
add_filter( 'plugin_action_links_' . plugin_basename( __FILE__ ), 'wc_gateway_custom_plugin_links' );
function wc_gateway_custom_plugin_links( $links ) {
$plugin_links = array(
'' . __( 'Configure', 'payment_cod2' ) . ''
);
return array_merge( $plugin_links, $links );
}
add_action( 'plugins_loaded', 'wc_gateway_cod2_init', 11 );
function wc_gateway_cod2_init() {
class WC_Gateway_COD2 extends WC_Payment_Gateway {
public $domain; // The text domain (optional)
/**
* Constructor for the gateway.
*/
public function __construct() {
$this->domain = 'payment_cod2'; // text domain name (for translations)
// Setup general properties.
$this->setup_properties();
// Load the settings.
$this->init_form_fields();
$this->init_settings();
// Get settings.
$this->title = $this->get_option( 'title' );
$this->description = $this->get_option( 'description' );
$this->instructions = $this->get_option( 'instructions' );
$this->enable_for_methods = $this->get_option( 'enable_for_methods', array() );
$this->enable_for_virtual = $this->get_option( 'enable_for_virtual', 'yes' ) === 'yes';
add_action( 'woocommerce_update_options_payment_gateways_' . $this->id, array( $this, 'process_admin_options' ) );
add_action( 'woocommerce_thankyou_' . $this->id, array( $this, 'thankyou_page' ) );
add_filter( 'woocommerce_payment_complete_order_status', array( $this, 'change_payment_complete_order_status' ), 10, 3 );
// Customer Emails.
add_action( 'woocommerce_email_before_order_table', array( $this, 'email_instructions' ), 10, 3 );
}
/**
* Setup general properties for the gateway.
*/
protected function setup_properties() {
$this->id = 'cod2';
$this->icon = apply_filters( 'woocommerce_cod2_icon', '' );
$this->method_title = __( 'Cash on delivery', 'woocommerce' );
$this->method_description = __( 'Have your customers pay with cash (or by other means) upon delivery.', 'woocommerce' );
$this->has_fields = false;
}
// and so on (the rest of the code)…
}
}
You can unset / remove original COD payment gateway changing the 1st function like:
add_filter( 'woocommerce_payment_gateways', 'wc_custom_add_to_gateways' );
function wc_custom_add_to_gateways( $gateways ) {
$gateways[] = 'WC_Gateway_COD2';
unset($gateways['WC_Gateway_COD']; // Remove COD gateway
return $gateways;
}