显示弹出消息在php中不起作用

Question

if($lresult>0)
        {
            $sql = "DELETE FROM orders WHERE orderID = '". $currentOrder['orderID'] ."'";
            $result = mysqli_query($dbConnect, $sql) or die(mysqli_error($dbConnect));
            echo "<script type='text/javascript'>alert('Some of your order was cancelled due to its one day time limit!')</script>";


        }

问题出在我回显警报消息的行中。它没有显示，但是当我尝试其他php文件时，它可以工作。该代码有什么问题？