This has been a feature of PHPUnit for some time but has been released as a separate project in the phpunit pear channel. The nature of PHPUnit means that many of these statistics can be collected while the tests are running, which is why it was added to that tool in the first instance.
Stats gathered include the number of directories, files, interfaces, methods, functions and constants with more details for each (like visibility, actual lines of code contained in them and the cyclomatic complexity). The tool is very simple to use - just call it from the command like and give it a path to your codebase. It does the rest and spits out a text-based report.