Test if PHP Session Variables are working.

test_php_session_vars.php

<?php
/**
 * Test if PHP Session Variables are working.
 * Step 1: Add this code into a custom plugin or in a PHP file you know is being executed.
 * Step 2: Navigate to /?test=123. You should see a blank old value and 123 as the new value.
 * Step 3: Navigate to /?test=456. You should see 123 as the old value and 456 as the new value.
 * If you see a blank old value again, that means that session variables are not enabled or otherwise broken.
 * If the timestamp at the top is not being updated, the page may be cached. 
 * Step 4: Remove this code.
 */
if(!empty($_REQUEST['test'])) {
	session_start();
	echo date('y-m-d h:i:s') . '<br />';
	echo 'Old value: ' . $_SESSION['test'] . '<br />';
	$_SESSION['test'] = $_REQUEST['test'];
	echo 'New Value: ' . $_SESSION['test'] . '<br />';
	exit;
}