$_session variable?

Hey,

I`m building a website ..

Ånd I have to show combobox.. when user is admin, it has to show different options..

So I check that with - if(!$_SESSION['isAdmin']): - then it shows options that are for normal user

And I have row in my table called "isAdmin" and by default it is NULL.. For admins I suppous I just write what I want, and it should anyway do anything thats written after else

I have start session in the beginning of page and script that connects to database, and login panel in every page.. So I log in with my account that has "isAdmin" filled in (with value - Y) .. So, when I check if(!$_SESSION['isAdmin']):, it should return false and do what`s after else ..

But it doesn`t.. I tryed to echo the variable.. But it shows nothing, as it was empty string..

What do I have to add to the script ? In other pages i`ve used this for checking if user is logged in, and it works...