Check whether a PHP session exists or expired using AJAX

Question

How to set the php session time out, I'm trying like below, but I dont think it works

ini_set("session.gc_maxlifetime", 600);
How to find out whether a php session exists or expired using ajax (javascript)?

Regards

Dunno about the first but the second is not really possible: if you send AJAX requests on regular intervals you keep the session alive for good. — Shadow The GPT Wizard, Apr 08 '11 at 19:02
@Shadow - while technically true if the session is cleared then a new session is recreated. He can use AJAX to check for a specific value — Cfreak, Apr 08 '11 at 19:10
@Cfreak true, but if the AJAX is sent every minute for example, it will keep the session alive forever as far as I can tell. — Shadow The GPT Wizard, Apr 08 '11 at 19:12
The session wouldn't get cleaned up if the AJAX script pings at an interval shorter than the expiring limit. however, the session will not just vanish after the timeout period. It's a probabilistic function, and can live anywhere from 0 hits to infinite hits AFTER the expiry time. — Marc B, Apr 08 '11 at 19:36

score 9 · Answer 1 · answered Apr 08 '11 at 19:07

For #1 use session_set_cookie_params(). To expire after 600 seconds

session_set_cookie_params(600)

(note unlike the regular setcookie function the session_set_cookie_params uses seconds you want it to live, it should not be time() + 600 which is a common mistake)

For number 2 just make a small script called through AJAX:

<?php
session_start()

if( empty($_SESSION['active']) ) {
     print "Expired"
}
else {
     print "Active"
}

?>

On the Javascript side (using JQuery)

$.get('path/to/session_check.php', function(data) {
     if( data == "Expired" ) {
         alert("Session expired");
     } else if (data == "Active" ) {
         alert("Session active");
     }
 });

score 2 · Answer 2 · edited May 23 '17 at 12:14

What Shadow Wizard commented about keeping the session alive every time you do the check is true.

But the solution is quite simple. The trick is to perform the AJAX request at an interval larger than the session life time. So if you establish a session timeout of 15 minutes you can check via AJAX every 16 or more.

In order for the above to work, the session timeout is something that you should implement manually. You can read this usefull answer on how to set the session duration.

Hope this helps you or anyone who is looking for the same!

Check whether a PHP session exists or expired using AJAX

2 Answers2