在WooCommerce中设置自定义日期字段的默认值

function add_custom_date_field($fields) {
    $fields['billing']['custom_date'] = array(
        'type' => 'date',
        'label' => __('Custom Date', 'woocommerce'),
        'required' => true,
        'class' => array('form-row-wide'),
        'clear' => true,
    );

    return $fields;
}
add_filter('woocommerce_checkout_fields', 'add_custom_date_field');

function set_custom_date_default_value($order_id) {
    $custom_date = isset($_POST['custom_date']) ? sanitize_text_field($_POST['custom_date']) : '';

    if (!empty($custom_date)) {
        update_post_meta($order_id, 'Custom Date', $custom_date);
    }
}
add_action('woocommerce_checkout_update_order_meta', 'set_custom_date_default_value');

function display_custom_date_default_value($order) {
    $custom_date = get_post_meta($order->get_id(), 'Custom Date', true);

    if (!empty($custom_date)) {
        echo '<p><strong>'.__('Custom Date').':</strong> ' . $custom_date . '</p>';
    }
}
add_action('woocommerce_admin_order_data_after_billing_address', 'display_custom_date_default_value');