Christian Weiske set out on a project - no small thing - to convert the current PEAR documentation info over to the PhD DocBook rendering system. In a new post he talks about the conversion process and some of the technology involved.
The reason for PhD to exist was that the previously used DSSSL based system was slow: a full build (all formats and all languages) took 24 hours to complete. Further, the tools the system based on were old, rusty and nobody understood why they broke on some machines, but also why they worked on other ones. Having a php-based system for PHP ensures that there is always someone around who can fix it if it's broken. This wasn't the case with the old documentation build system.
The conversion was spurred on by the fact that the PEAR documentation stopped building and more and more people were finding it hard to build on their machines too. He walks through the steps he took - installing PhD, converting over the docs to the DocBook 5 format and the first builds with the new system.
Now that at the XML was shiny, too, it was time to actually use PhD on it. The numbers were amazing: While a build for one format and one language took around 40 minutes on my system (dual core Macbook with 2GHz and 2GiB RAM), building the same with PhD takes 45 seconds!