phpScenario is an object-oriented and open source PHP library for implementing simple A/B testing with as little code as possible but still being powerful.

Default tests can be ran with only a single line of code and results are rendered XML-based (HTML via 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.