If you've been looking for a way to get those transactions in MySQL 4.0 working with your site, then this new piece from DevArticles might be just what you need.

In one of their latest, Using Transactions with MySQL 4.0 and PHP, the author details how you can use a local MySQL server (running 4.0.12, obviously) to create a "trans" table to perform the transactions on. They show you what the BEGIN, COMMIT, and ROLLBACK functionality is for, as well as show you how to use it inside of PHP (the point of it all).

These new features can lead to all sorts of new applications in scripts, especially in things like shopping carts, or something where keeping track of a list temporarily might be a Good Thing.