Andreas Heigl with the PHP core team announced that the PHP-Documentation project is now using Git over SVN with the goal of it being easier for everyone to contribute. If you’d like to get started they have a guide available on Github.
From the Github readme here is what you need to get started:
If you are interested in information about how to set up the tools needed, how to work with Git and DocBook on Linux or Windows, or what conventions you should follow when writing phpdoc files, please refer to the PHP Documentation HOWTO.
You can read the HOWTO online at: http://doc.php.net/tutorial/
If you are already working with the phpdoc module, then you can find its XML source in the howto directory of the module, and build it yourself with:
phd -d .manual.xml
However, PhD is a separate project which can be read about here: https://wiki.php.net/doc/phd