我已根据以下内容在装运方法中创建了自定义文件：

function shipping_instance_form_add_extra_fields($settings)
{
    $settings[\'shipping_extra_field\'] = [
        \'title\' => \'Route Number\',
        \'type\' => \'text\', 
        \'placeholder\' => \'1,2,3...\',
        \'description\' => \'Enter route number\'
    ];

    return $settings;
} 

我需要在订购时将路由器号添加到订单中，它可以更改后订单这就是我将其保存到订单中的原因。我尝试了以下方法，但没有任何乐趣：

add_action( \'woocommerce_after_order_notes\', \'my_custom_checkout_field\' );

function my_custom_checkout_field( $checkout ) {

    echo \'<div id="my_custom_checkout_field" style="display:none;"><h2>\' . __(\'Route Number\') . \'</h2>\';

    woocommerce_form_field( \'route_number\', array(
        \'type\'          => \'text\',
        \'class\'         => array(\'my-field-class form-row-wide\'),
        \'label\'         => __(\'Fill in this field\'),
        \'placeholder\'   => __(\'Enter something\'),
        ), $checkout->get_value( \'route_number\' ));

    echo \'</div>\';

}


add_action( \'woocommerce_checkout_update_order_meta\', \'my_custom_checkout_field_update_order_meta\' );

function my_custom_checkout_field_update_order_meta( $order_id ) {
$shipping_methods = WC()->shipping->get_shipping_methods();
$shipping_method = @array_shift($order->get_shipping_methods());
$shipping_method_route_number = $shipping_method[\'Route Number\'];
update_post_meta( $order_id, \'Route Number\', sanitize_text_field( $shipping_method_route_number ) 
}

欢迎任何帮助

add_action(\'woocommerce_init\', \'shipping_instance_form_fields_filters\');

function shipping_instance_form_fields_filters()
{
    $shipping_methods = WC()->shipping->get_shipping_methods();
    foreach($shipping_methods as $shipping_method) {
        add_filter(\'woocommerce_shipping_instance_form_fields_\' . $shipping_method->id, \'shipping_instance_form_add_extra_fields\');
    }
}

function shipping_instance_form_add_extra_fields($settings)
{
    $settings[\'route_number\'] = [
        \'title\' => \'Route Number\',
        \'type\' => \'text\', 
        \'placeholder\' => \'1,2,3...\',
        \'description\' => \'Enter route number\'
    ];

    return $settings;
} 

add_action( \'woocommerce_checkout_update_order_meta\', \'my_custom_checkout_field_update_order_meta\' );

function my_custom_checkout_field_update_order_meta( $order_id ) {
         $chosen_methods = WC()->session->get( \'chosen_shipping_methods\' );
    $chosen_shipping = substr( $chosen_methods[0],-1);
         $free_shipping = get_option( \'woocommerce_free_shipping_\'.$chosen_shipping.\'_settings\' ); 
        $route_number    = $free_shipping[\'route_number\'];

        update_post_meta( $order_id, \'Route Number\', sanitize_text_field( $route_number ) );

}