Confused about sessions

I have read all that I can find on sessions. It seems that the more I read the less I understand. Go figure. I have a cart I am working on and it works excellent, except I can not get the session to end. Here's what I have: //Track Session session_start(); if ((!$PHPSESSID) || (!$item_count_total)) { session_register("item_count_total"); } if (!$item_count_total) { $item_count_total = "0"; } Then I try to end the session, shortly after this statement on the checkout page, with: //End session session_destroy(); But, I can still view the cart after checking out. I think that php may be writing a cookie somewhere, but I don't where/what. I got the first piece of code from a book. Is is writing a variable called $item_count_total, and I need to session_unregister("item_count_total");? Any ideas?????