symfony/symfony-docs — pull request #1582 by lyrixx (2012-07-20 11:25:57+00:00)
Title: Fixed typo in cookbook/event_dispatcher/class_extension.rst

see https://github.com/symfony/symfony/blob/master/src/Symfony/Component/EventDispatcher/EventDispatcher.php#L164

the second argument of `$dispatcher->addListener` must be callabled. so I think it is a typo.