$baseurl

Hi,
I have a problem with detect of $baseurl. When I use session I can check if the user is authorized, but how can I detect which section can I open?
For example I have two sections (e.g. News and Articles) and I have for each of section different folder in "userfiles". I can't use sessions for this, because user can open each section in new window and work with them at random (in session can I save only one of section - the latest).

Have you an idea?