Undefined index: ref

v2.2

PHP Notice: Undefined index: ref in /path/to/wp-content/plugins/goaffpro/goaffpro.php on line 95

In:

/**
 * Add goaffpro referral cookie in woocommerce order metadata if referral cookie is available.
 * This helps in tagging the orders received with the unique ID of the affiliate who sent the customer
 */
add_action('woocommerce_checkout_update_order_meta',function( $order_id, $posted ) {
	$referral_code = sanitize_text_field($_COOKIE['ref']);
	if($referral_code){
		update_post_meta($order_id, 'ref', $referral_code);
	}
} , 10, 2);

Fix with:

add_action('woocommerce_checkout_update_order_meta',function( $order_id, $posted ) {
	if( ! isset( $_COOKIE['ref'] ) ) {
		return;
	}
	$referral_code = sanitize_text_field($_COOKIE['ref']);
	if($referral_code){
		update_post_meta($order_id, 'ref', $referral_code);
	}
} , 10, 2);