On the Liip blog there's a new post that compares some of the popular PHPDocumentor-formatted comments parsers. They're looking specifically at the support for interfaces, not just the usual classes and methods.

The interfaces define the standard and are extensively documented. The implementation was built by copying the interfaces and implementing the methods. Now we have the documentation comments duplicated, which is a pain to maintain if we clarify or change anything in the interfaces documentation. [...] In PHP, there is a couple of doc compilers. While they basically all follow the same syntax as Java uses, none of them gets everything right unfortunately.

The four covered are PhpDoctor, DocBlox, PHPDoc and Doxygen. They look at things like namespace support, the inheritance information they generate and if it correctly uses the "@inheritDoc" tagging functionality.