shopping cart

Hi I listed my shopping cart in this form: product_name quantity(text field in form) price And I want allow user to change quantity and then after submit load cart contents with new quantity. I forward text value in one variable(name of text field) and id of product in second(hidden type) to my php script which modify quantity in mysql table. This is working good but only if I have one product in cart . What should I do to forward to script all variables of products in cart. My modify function is part of class and when I put there global $HTTP_POST_VARS; variables of that one product weren't be seem , if I write global $id,$quantity they were been seem very well ( but it's still for one product). How to make $HTTP_POST_VARS been see in class function? thx for any help sasza