判断 if isset empty

if (empty($order_id) || empty($action_array))
    {
        return $return_res;
    }

 if (!isset($operable_list['remove']))
    {
        make_json_error('Hacking attempt');
        exit;
    }

elseif ($action == 'del_order')
{

    $order_id = isset($_REQUEST['order_id']) ? intval($_REQUEST['order_id']) : 0;
    if ($order_id == 0)
    {
        $err -> show($_LANG['booking_list_lnk'], 'user.php?act=booking_list');
    }

    if ($user_id == 0)
    {
        /* 用户没有登录 */
        $err -> show($_LANG['booking_list_lnk'], 'user.php?act=booking_list');
    }

    /* 检查订单是否属于该用户 */
    $order_user = $db->getOne("SELECT user_id FROM " .$ecs->table('order_info'). " WHERE order_id = '$order_id'");
    if (empty($order_user))
    {
        $err -> show($_LANG['booking_list_lnk'], 'user.php?act=booking_list');
    }
    else
    {
        if ($order_user != $user_id)
        {
            $err -> show($_LANG['booking_list_lnk'], 'user.php?act=booking_list');
        }
    }

    /* 删除订单 */
    $sql = "delete i,g,a from " .$ecs->table('order_info'). " as i join " .$ecs->table('order_goods'). " as g on i.order_id = g.order_id join " .$ecs->table('order_action'). " as a on i.order_id = a.order_id where i.order_id = '$order_id'";
    $message = $db->query($sql);

    if ($message === true)
    {

        show_message('删除成功', $_LANG['back_booking_list'], 'user.php?act=order_list', 'info');

    }
    else
    {
        $err -> show($_LANG['booking_list_lnk'], 'user.php?act=booking_list');
    }
}