有条件地将自定义结帐字段添加到WooCommerce中的发货部分

function add_custom_checkout_field($fields) {
    $fields['shipping']['custom_field'] = array(
        'label'       => __('Custom Field', 'woocommerce'),
        'placeholder' => _x('Custom Field', 'placeholder', 'woocommerce'),
        'required'    => false,
        'class'       => array('form-row-wide'),
        'clear'       => true
    );

    return $fields;
}
add_filter('woocommerce_shipping_fields', 'add_custom_checkout_field');

function display_custom_checkout_field($order){
    echo '<p><strong>'.__('Custom Field').':</strong> ' . get_post_meta($order->id, '_custom_field', true) . '</p>';
}
add_action('woocommerce_admin_order_data_after_shipping_address', 'display_custom_checkout_field', 10, 1);

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