An Open Source XML Publishing Framework for PHP 5
Popoon is an open source XML Publishing framework. It's modelled after Cocoon and is completely written in PHP 5.
Popoon is the publishing backend within Flux CMS, but it can be used independently from the CMS.
Christian Stocker gave a speech about popoon at the PHP Conference in Frankfurt 2002. You can see the slides and some examples here:
http://old.chregu.tv/popoon/pres/ (firefox needed)
You can get popoon via Subversion:
Popoon is an open source project (Apache Software License 2)