How Can I Securely Identify AJAX Requests in PHP?

Securely Detecting AJAX Requests in PHP

Checking if an incoming request is an AJAX request is crucial for server-side processing. While methods like GET parameters or headers can be easily exploited, a more secure approach is available.

Solution: HTTP_X_REQUESTED_WITH Header Check

The HTTP_X_REQUESTED_WITH header is a standard header sent by AJAX requests. This header is typically set to "XMLHttpRequest" or "xmlhttprequest." By checking this header, you can reliably identify AJAX requests:

<code class="php">if(strtolower($_SERVER['HTTP_X_REQUESTED_WITH'] ?? '') === 'xmlhttprequest') {
    // We can assume that the request was made with AJAX
}</code>

Example Usage

Consider a PHP script, mypage.php:

<code class="php"><?php

if(strtolower($_SERVER['HTTP_X_REQUESTED_WITH'] ?? '') === 'xmlhttprequest') {
    // Process AJAX request
} else {
    // Not an AJAX request
}

?></code>

This script checks if the HTTP_X_REQUESTED_WITH header exists and is set to "XMLHttpRequest." If it is, it assumes the request is an AJAX request and proceeds to process it accordingly. Otherwise, it handles the request as a non-AJAX request.

Advantages

This method is secure because the HTTP_X_REQUESTED_WITH header is sent automatically by the browser for AJAX requests. It cannot be easily faked by attackers. Additionally, it is supported by most modern browsers and server platforms.

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