PEAR is the PHP Extension and Application
This manual is written in XML using the DocBook XML DTD, using DSSSL (Document
Style and Semantics Specification Language) for formatting. The
tools used for formatting HTML versions are
Jade, written by James Clark and The Modular DocBook Stylesheets
written by Norman Walsh.
The basic structure is based on the great work already done by the PHP
documentation group. Read About
the PHP manual for more details.