Using this article from Johannes Schluter as a starting point Vinu Thomas has worked up his own example of how the technique is used in the example on the Launchpad page.

This article is interesting because of the uses which come up when you can create custom Storage Engines using PHP. An interesting usecase for this is in creating test cases, where you can feed the data for a query from PHP and trap the activities on the database.

The example code defines methods for update, write and delete and the SQL to create the table and insert/manipulate rows is included (for a table created with "ENGINE=PHP").