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

change the session name at the top of the core functions file like

 session_name('mysession');

then use the following code into the php page

  session_set_cookie_params(0,"/",".example.com",FALSE,FALSE);
  setcookie(session_name(), session_id(),0,"/","example.com");
  session_start();

finally change the default session name of the subdomain and remove the default cookie in subdomain's core functions file like:

 /*default session name*/
 session_name("mysession");
 /*remove the PHPSESSID and default session name from subdomain's cookie*/
 setcookie( "mysession", "",1,"/" );
 setcookie( "PHPSESSID", "",1,"/" );

if you continue with using your cookie name as PHPSESSID ,just remove all the functions with

 "mysession" string like session_name('mysession'), setcookie( "mysession", "",1,"/" );

then check your browser's existing cookies, just remove all the cookies of domain and subdomain, and repeat the process.