session_destroy problem

Hi there, I have written a class that manages sessions. I have never used sessions before so all this is new to me. Everything works fine as far as starting the session and logging in however when I call sessoin destroy it doesn't seem to work the function returns 1 as it should if all goes well however if I go to another page and do some other browsing even if I close the browser the session still hangs around. Is there something I don't know about sessions? I have read the documentation on the session_destroy function, I don't think that I am missing anything... Anyone have any suggestions? I am totally confused. Thanks Ken