Simple loop calculations

Greetings, I need some help with [login to view URL] I am developing an shopping card'ish solution - its more like a user individual product list that are predefined to him. Explaining the code. User chooses some products $user , the are added to the basket, after posting the script would determin which products he could afford within the given budget $userBudget, It loads also the products from the database and compares the values. Current state of the script does not includes the budget functionality due to my lack of ideas how to place it. $amountToPay,$new_still_to_pay,$new_paid_amount would be needed to calculated by using the user budget. Ready to run and test code : [login to view URL]