in reply to Shopping Cart
My simple answer is no. A shopping cart implies a lot of things. Let's start by making the arbitrary assumption that you already have a way to process completed orders. This means you have a secure, working way to take some message sent from your system and process the credit card info from it (again securely) and turn that into a real order that will be shipped and tracked and so on.
Assuming you have that all wrapped up, then what you're asking about is a way to create and store and deliver that message to the magical order processing system. What that boils down to is maintaining state. This is something many wiser than I have covered:
What you're task is is to take some token - an id with password, an email address - and associate that with some list of values - the items in the cart. You may want to make it simple, i.e. you create as you go and then you check out or dump it. Or you may want people to be able to shop a bit now, shop a bit later. The more features means the more complexity.
"A man's maturity -- consists in having found again the seriousness on +e had as a child, at play." --Nietzsch +e