In his latest post, Sebastian Bergmann mentions the work he's done to integrate Selenium with PHPUnit to make a powerful testing platform.

Today I committed the initial work for integrating Selenium RC with PHPUnit. In this case it is PHPUnit that drives the execution of the web application UI tests, using PEAR's new Selenium package to communicate with the Selenium RC Server.

He includes an example of how it will be used, creating a test to check if a page's title is equal to "Example Web Page".