The Script phpScenario is an object-oriented and open source PHP library for for Developers, implementing simple A/B testing with as little code as possible.
The default tests can be ran with only a single line of code and the results are rendered XML-based (HTML via an included XSL stylesheet).
The library supports PDO and Zend Framework DBALs. Also, it has various options for running more customized tests like using identifiers other than PHPSESSID.