ok, forget what I said about passwords in the $_SESSION variable... that doesn't make much sense (I'm not getting nearly enough sleep these days!)...
what you want to do is when a user logs into protected area #1, set a session variable like: $_SESSION['access1']='logged in'
In each of the protected pages in area1, only display the content if $_SESSION['access1']=='logged in', else give a 'you must log in' message.
Same goes for access area #2.
When the user logs out of area #2, either unset $_SESSION['access2'] or change its value to 'logged out'.