Allow php sessions to carry over to subdomains

Question

I use php sessions (not cookies, except for session id cookie) for all user data, and when a user goes to their profile user.mydomain.com they are immediately \"logged out\"

Answer 1

if(isset($_COOKIE['session_id']))
    session_id($_COOKIE['session_id']);
    Zend_Session::start(); //or session_start();

    if(!isset($_COOKIE['session_id']))
        setcookie('session_id', session_id(), 0, '/', '.yourdomain.com');

This is a good solution, but you cannot use it in all situations. For examples it will not work when you cannot rely on not-session cookies.

This actually MUST work if you use it correctly.

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

For example you need to put it before session_start() and also in all files that call session_start()