Here are a few question-based titles that capture the essence of your article: * How to Implement File Size Validation in JavaScript and PHP? * Client-Side vs Server-Side: Best Practices for File Siz

Check File Size Before Upload

Your current JavaScript script effectively validates the file extension of user-uploaded images. To additionally check the file size and prevent uploads larger than 500 KB, you can incorporate the code you found:

<code class="javascript">function checkFileSize(inputFile) {
  var max = 3 * 512 * 512; // 786MB

  if (inputFile.files && inputFile.files[0].size > max) {
    alert("File too large."); // Do your thing to handle the error.
    inputFile.value = null; // Clear the field.
  }
}</code>

Client Side Validation

This checks the file size before the user submits the form, providing a client-side validation. However, keep in mind that client-side validation can be tampered with, so it's crucial to implement server-side validation as well.

Server Side Validation

On the server, you can utilize PHP to validate the file size. The $_FILES array provides information about uploaded files. The following PHP code demonstrates how to validate the file size:

<code class="php">if(isset($_FILES['file'])) {
  if($_FILES['file']['size'] > 500000) { // 500 KB
    // File too large
  } else {
    // File within size restrictions
  }
}</code>

Combining Client and Server Side Validation

To ensure robustness, combine both client and server side validations. This protects against potential client-side tampering, guaranteeing that files larger than the established limit are not uploaded.

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