I'm not sure you can do that.. A client has a session_ID until either A)Session timesout, 😎Session is destroy or unset c)Client closes the broswer and opens a new one.
The only way I can think of is check to see if a session is set first and if it is change the name..
$session_name = 1;
if (isset($_SESSION[$session_name])){
$session_name = $session_name+1;
}
Then just refer to your session by the var..