VbzCart/session

Note
This documentation was last edited in 2008, and should be checked for accuracy.

About
A session is when a particular user is connected to VbzCart using a particular browser on a particular computer.

Multiple carts may be created in a single session, as well as multiple orders. The same cart may not be accessed from different sessions; the user needs to save the cart to something which can be identified humanly, i.e. an order (or, in the future, perhaps a wish list).

A session also helps keep track of user preferences, e.g. searching only certain item types or topics.

Identifying a Session
I've been debating about the idea of allowing carts to work using IP address/domain plus browser ID (user_agent) because cookies don't always seem to work (and some people have them turned off), and I think I've come up with a reasonable compromise.

The problem is that one user might connect through a dial-up (dynamic IP), place orders in a cart and disconnect, and then another user with the same browser and OS might happen to connect through the same dial-up -- which would cause that user to be assigned the previous user's shopping cart. This isn't a serious problem, because no personal information will be conveyed, but it can be off-putting to go to a store and find that your cart already has items in it. I would be inclined to immediately go somewhere else if I encountered this.

What I've come up with is the following:
 * sessions IDed via IP/browser have a much shorter expiration than cookie sessions
 * sessions IDed via IP/browser will show a warning to indicate the shorter expiration time (should show the time when the session will expire -- and the current time, to prevent timezone confusion)
 * cookies have never been used for checkout; we have always used POST data (?session=xxxxx), so that's not an issue

Sequence of Events

 * On receiving one or more items to add to the cart:
 * Try to match with existing session:
 * Check for session cookie; if found, use that
 * If no session cookie, look for unexpired IP/browser match
 * If no usable existing session found, create a new one (empty cart)
 * Add items to the session cart
 * Display cart & session info