PHP native session issue on expressionengine

Question

I am using sessions for my expressionengine project. I have used the following methods to set sessions at the top of the page.

    if (session_id() == ''){
         session_start(); 
    } or

   if(!isset($_SESSION)){
        session_start();
    }

      or

   if(empty($_SESSION['userid'])){
      session_start(); 
   } 

I have written custom expression engine plugin where I do session check.

After sometime I observed a strange behaviour of sessions. It is getting set different for different url. for http:// url it sets differently and for www:// url it sets differently. How do I set and retrieve sessions such that both http://example.com and www.example.com will yeild same result.

I have followed steps from this url as well http://ellislab.com/forums/viewthread/231468/. I have posted the same issue on http://ellislab.com/forums/viewthread/232604/. But its not helping me.

Can someone help me on this.

Answer 1

Thanks @mishu. After you explained that www was a subdomain and a session_cookie problem, I did some experimentation and then googled a bit.

This post on stackoverflow was very helpful. PHP Sessions across sub domains

I opened the index.php file on root folder of expressionengine / codeigniter and then added the below line

ini_set('session.cookie_domain','.example.com');

Now its working fine. If someone could explain briefly on this thread, it will be of great use to other developers.