PHP session interfering with sub-domain session

Since they share the same domain, they are the same site and share a session.

You can manually override this by using session_name in your admin section.

Something like this:

<?php
//this forces the admin page to recognize a different cookie as it's session id
session_name('PHPADMINSESSID');

//start the session normally
session_start();

There are a few other tricky ways to do this, but you should generally avoid tricky, because you can easily forget what you did and not be able to figure it out later. I will explain some of those also for reference though:

• Dual subdomains alter the expected hostname if they can be used, and will cause two different inherent sessions. For example subdomain.example.com and example.com will share a session, but subdomain.username.example.com and example.com will not, and will use separate sessions. You should avoid this, because if you decide to implement some backend logic to manage the session and expect them to be shared, this will become very difficult to work around.

• You can also force different sessions using session_id, but this requires that you manually track the id's and will get quite convoluted, and will also require you to set up some sort of data store to keep track of which sessions go to what, which adds a lot of unnecessary overhead.

Easiest way is to just use different session_name values for each session.