Francesco Montefoschi has a recent post to his blog looking at a tool you could use to ensure the quality of your code comments - PHPADD, the abandoned docblock detector.

PHPADD can analyze a directory with PHP source code and detect (for each file, for each class, for each method) if the parameters in the function declaration are compatible with the parameters found in the docblock, reporting the outdated ones. This can be easily integrated in your build script and the result can be published in build result. Using Hudson, you just need HTML Publisher plugin.

The include the (super simple) installation instructions for pulling it in via the PEAR installer and running it on your codebase. There's even some sample output included. If you're interested in the source, check out (or fork) the latest code on github.