Like Action Helpers, which I've discussed in a previous article, Front Controller Plugins in Zend Framework are often considered an esoteric, advanced subject. They are, however, remarkably simple to implement, and provide an easy way to extend the functionality and behavior of your entire web application.

The article (from Matthew Weir O'Phinney) looks at the hooks defined in the controller, like routeStartup and preDispatch, and how to work with the controller to add in/get plugins from it. He provides a two examples too: Application Initialization Plugin and a Caching Plugin.

Zend_Controller_Plugin is not covered yet in the documentation but it is a powerful way of extending a controller. Briefly, Zend_Controller_Plugin is used for extending controller functionality by attaching listeners to events, which are fired (or trigged) by the controller classes.

He talks about the plugin interface, how it hooks into the controller and defines the relationship with some pseudo-code (showing implements versus extends). There's talk of the Zend_Controller_Plugin_Broker class and the Zend_Controller_Front. He looks in detail at this last class, showing how it helps to handle incoming requests for the plugin functionality and veen includes working code you demonstrate how.