Javascript + PHP/MySQL powered online cart

A very simple test of ajax and PHP powered cart, for my personal website.
Cart content is stored in PHP sessions, and its display is live-updated with AJAX.
I used Prototype for AJAX calls, guess I could also use it for other things to reduce the code... like with getElelemtByClassName() or something...).

• Javascript only for now, but making it non-javascript-browsers-OK would be (and will be) very easy.
• Only one item of each in cart.
• No check-out, nothing, just the cart.
• No taxes, sending fees, etc. for now (guess I'll add this when I'll do the checkout thing)
• No "one-item-page", no categories, no tags, etc.

The related-post in my blog is here (in french).