Ladder is a (deprecated) database migration system for MySQL databases, written in PHP.
Its replacement, Ladder v2 is in progress, using Symfony components and PDO.
What's A Migration System?
You keep your source code in a version control system like Mercurial, Git, or Subversion, right? Well, how do you track (and monitor) the state of your database along with that code? That's the problem Ladder aims to solve.
By keeping its state in the database (using a configurable table), Ladder allows multiple developers to work on the same database, without overwriting each others changes.
Ladder will show what commands are availble when you run it with no parameters. To get a copy, head over to the Source page. Once you've downloaded it, take a copy of ladder.php.sample, name it ladder.php, follow the same procedure with the sample files in the config/ directory. Open up the files you just created, and plug your details in.