DocBlox is the new defacto PHP class documentation generator. It was developed as an alternative to PHPDocumentor, but it looks as though it will replace it and become the new PHPDocumentor2. As a result I thought I would put together a quick tutorial on getting started.
This post assumes that you know what PHPDoc comments are and that you have a project that you want to generate API documentation for. To get started on PHPDoc take a look at the Wikipedia page on PHPDoc.
Whereas PHPDocumentor would scan and generate all of the code in one go, DocBlox will scan the source code and generate a series of XML files based on the code it finds. It will then use these files to generate the API documentation in a number of different formats, although HTML is probably the most common.