I am making a trading website and am trying to make users to upload ads. The code that i have written is running fine with no errors when i run it on localhost. But when i hosted the site and then tried to upload the ad i got "500 internal server error". I have made no changes to the code.
submitad file
<html>
<head>
<title>Submit Ad</title>
<link rel="stylesheet" type="text/css" href="css/signup.css"/>
</head>
<?php
require('heading.php');
?>
<form class="submit-ad" action="submitad_validation.php" method="POST" enctype="multipart/form-data">
    <h1 class="sign-up-title">Submit Ad</h1>
    <input type="text" name="title" class="sign-up-input" placeholder="Title" required  autofocus>
    <input type="text" name="description" class="sign-up-input" placeholder="Description" required>
    <input type="text" name="contact" class="sign-up-input" placeholder="Email ID" required>
    <input type="text" name="price" class="sign-up-input" placeholder="Expected Price" required>
    <select class="sign-up-input" name="categories" required>
      <option value="mobile">Mobiles and Accessories</option>
      <option value="laptop">Laptops and Accessories</option>
      <option value="cars">Cars</option>
      <option value="bikes">Bikes</option>
      <option value="appliances">Home Appliances</option>
      <option value="books">Books</option>
      <option value="jewelery">Jewelery</option>
      <option value="music">Musical Instruments</option>
      <option value="pets">Pets</option>
    </select> 
    <!-- Code to upload the image of the item -->
    <input type="file" name="imageUpload" id="imageUpload"> 
    <input type="submit" value="Submit Ad" name="submit" class="sign-up-button">
</form>  
</html>
submitadvalidation file
<!--This page is used to get the ad data from the user and then store it in the database-->
<?php
require('connection.php');
session_start();
$title=$_POST['title'];
$description=$_POST['description'];
$value=$_POST['categories'];
$price=$_POST['price'];
$contact=$_POST['contact'];
$id=$_SESSION['user_id'];
if(isset($_POST['submit']))
{
    //Process the image that is uploaded by the user
    $target_dir = "uploads/";
    $target_file = $target_dir . basename($_FILES["imageUpload"]["name"]);
    $uploadOk = 1;
    $imageFileType = pathinfo($target_file,PATHINFO_EXTENSION);
        if (move_uploaded_file($_FILES["imageUpload"]["tmp_name"], $target_file)) {
            echo "The file ". basename( $_FILES["imageUpload"]["name"]). " has been uploaded.";
        } else {
            echo "Sorry, there was an error uploading your file.";}
    $image=basename( $_FILES["imageUpload"]["name"],".jpg"); // used to store the filename in a variable
    //storing the data in your database
    $query= "INSERT INTO items VALUES ('$id','$title','$description','$price','$value','$contact','$image')";
    mysql_query($query);
    require('heading.php');
    echo "Your add has been submited, you will be redirected to your account page in 3 seconds....";
    //redirecting the user back to the account page after successful uploading of the ad
    header( "Refresh:3; url=account.php", true, 303);
}
?>
 
    