After studying mymarket code i'm trying to write a shopping cart of my own. I'm using the mymarket Cart class. I'm alittle confused as to how PHP keeps track of what item's the user has in their shopping cart and how PHP originally query's the database for which product id's are available. In cart_add.php it add's an item by calling..

$SESSION["cart"]->add($id, 1);

I have no idea what the "->" means lol. I'm pretty new. I'm guessing that $SESSION["cart"] is part of the session started and it's calling the Cart class for some reason. I'm also guessing that add() is a function defined in cart.php. All of this is cool but when I goto shopping_cart.php after I think i've added an item I get some error about $qid being undefined. I'm willing to deal with that, its ok, I just figured i'd write my own database query to display the item's in the shopping cart. Problem Is I don't know where to start! Could anyone be so kind as to help? I've been struggling with this for day's. If by this time i've confused you to the point where you have no idea what i'm talking about i'm sorry reach me on ICQ as 75138423 and I can try to explain better. If your struggling with the same sorts of problems contact me too and maybe we can work it out togethor. Thanks.