PHPDbMigrate is a database schema management library that allows you to add new changes to a database and if need be revert those changes. Those familiar with Ruby on Rails ActiveMigration procedures will find PHPDbMigrate very familiar.

A migration file consists of two sections: up; down. Within each section the lines that are entered instruct what changes to the database are needed. PHPDbMigrate in turn formats those instructions into proper SQL pertaining to the database you are using.

There are times that a complex query needs to be executed and PHPDbMigrate can handle those. PHPDbMigrate even handles running native PHP code blocks.

You can find the code base at: http://code.google.com/p/phpdbmigrate/