Rob Morgan has a recent post showing you how to use Phinx, a PHP-based database migration tool, to handle your database changes (both "up" and "down").
Earlier this year I decided to open-source one of my personal software projects - Phinx. Phinx is a database migration tool (think Ruby on Rails ActiveRecord migrations) where can you describe all of your database transformations in pure PHP. I have used this tool for many of my consulting projects, however it still took a lot of effort to turn it into a re-usable product. In this tutorial I'm going to explain how to install Phinx and use it with a simple guestbook application.
He uses a sample guestbook project for his example, showing how to get it all installed and how to create a migration that adds a "posts" table.