将自定义字段添加到自定义Woocommerce电子邮件

<?php
/**
 * Custom Email Template
 */

// Get order object
$order = wc_get_order( $order_id );

// Get custom field value
$custom_field_value = get_post_meta( $order->get_id(), 'custom_field', true );

// Output custom field value
if ( $custom_field_value ) {
    echo '<p>' . esc_html__( 'Custom Field:', 'your-theme-textdomain' ) . ' ' . esc_html( $custom_field_value ) . '</p>';
}
?>

/**
 * Custom Email Template for Order Completed Email
 */
add_filter( 'woocommerce_email_classes', 'custom_add_email_classes' );
function custom_add_email_classes( $email_classes ) {
    require_once( 'path/to/custom-email-template.php' );
    $email_classes['WC_Email_Customer_Completed_Order'] = new Custom_Email_Template();
    return $email_classes;
}

class Custom_Email_Template extends WC_Email_Customer_Completed_Order {
    /**
     * Custom Email Template Constructor
     */
    public function __construct() {
        $this->id             = 'customer_completed_order';
        $this->customer_email = true;
        $this->title          = 'Custom Completed Order';
        $this->description    = 'Custom completed order emails are sent to customers when their order is marked completed and contains custom fields.';
        $this->template_html  = 'emails/custom-email-template.php';
        $this->template_plain = 'emails/plain/custom-email-template.php';
        $this->placeholders  = array(
            '{site_title}'   => $this->get_blogname(),
            '{order_date}'   => '',
            '{order_number}' => '',
        );

        // Call parent constructor
        parent::__construct();
    }
}