How to Validate File Size Before Upload Using JavaScript and PHP?

Check File Size Before Upload

The provided JavaScript function effectively validates file types based on the _validFileExtensions array. To extend this functionality and check file size before upload, you can implement the following client-side JavaScript:

<script language='JavaScript'><br>function checkFileSize(inputFile) {<br>  var maxFileSize = 500 * 1024; // 500 KB (convert to bytes for comparison)</p>
<p>if (inputFile.files && inputFile.files[0].size > maxFileSize) {</p>
<pre class="brush:php;toolbar:false">alert("File too large."); // Display error message
inputFile.value = null; // Clear the input field

}
}

This code checks if the file size exceeds the specified limit in bytes. If it does, an error message is displayed, and the user is prompted to select another file.

In addition to the client-side validation, it is essential to implement server-side validation to ensure the file size restriction is enforced. This can be achieved using PHP's PHPMyCoder suggestion:

<?php<br>if (isset($_FILES['file'])) {<br>  $maxSize = 500 * 1024; // 500 KB (convert to bytes)<br>  if ($_FILES['file']['size'] > $maxSize) {</p>
<pre class="brush:php;toolbar:false">// Handle error: File too large

}
}

Remember that client-side validation can be bypassed, so server-side validation remains crucial for security and data integrity. By employing both client-side JavaScript and PHP, you can effectively check file size limitations before uploading, providing a more robust and secure file upload process.

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