note 29122 rejected from function.session-unregister by nicos

I read the notes but I'm confused. Some of the documentation specifically warns against using $_SESSION with, say, session_register. Does this mean you can't even access, say, $_SESSION['user'] ???? If so, it seems like session_register etc is only useful IF register_globals is on. Is that right ? Also, another note indicates that you're supposed to do: $_SESSION['user'] = NULL to remove a variable from the session store. But for me, using PHP 4.2.2, with register_globals off, this does NOTHING. The only way I can unregister a variable is to use session_unregister. But, since register_globals is off, it also seems ilke I HAVE to use $_SESSION. So how can I, if the instructions say I can't use BOTH session_unreigster and $_SESSION at the same time ?