Karsten Deubert has a recent post to his blog looking at annotations in Zend Framework applications to enhance functionality already in the framework.
Recently I had the idea to influence Controller Actions with annotations but discarded it with thoughts like "In PHP I will have to use reflection and some black magic to get this working which will have insane performance hits for my applications"... until I set everything up to see that it costs just 1-2ms in average per request without any form of caching.
He includes a few bits of code to show a simple annotation example (setting a layout) and the controller plugin that performs the translation. In his case, it's hard-coded to look for the "@layout" annotation in the docblock comment, but it'd be relatively trivial to extend it to a more full-featured version.