无法将行插入数据库中的表

Question

我正在尝试从表单中获取一些数据以将数据插入数据库。但是，在执行SQL语句后，它无法正确执行并引发错误。后来，我发现代码中的“ mysqli_real_escape_string（）”方法返回空字符串

<?php

$productName=$productDesc=$price=$newPrice=$message="";
$marketId="";
$cityId="";
if(isset($_GET['marketId'])&& isset($_GET['cityId'])){

$marketId=$_GET['marketId'];
$cityId=$_GET['cityId'];

}

if(isset($_POST['addProduct'])){



           //NOW INSERT THE ROW TO DATABASE
         $productName=mysqli_real_escape_string($conn,$_POST['productName']);
           $productDesc=mysqli_real_escape_string($conn,$_POST['productDesc']);
            $price=mysqli_real_escape_string($conn,$_POST['price']);
           $newPrice=mysqli_real_escape_string($conn,$_POST['newPrice']);

           $marketID=mysqli_real_escape_string($conn,$marketId);

           $cityID=mysqli_real_escape_string($conn,$cityId);

           $sql="INSERT INTO products(productName,productDesc,price,newPrice,imgUrl,marketId,cityId) VALUES('$productName','$productDesc','$price','$newPrice','$fileDestination','$marketID','$cityID')";


           if(mysqli_query($conn,$sql)){
            $message="success";

           }
           else{
             $message="error";  
           }


}