Processing the Output Buffer with XSLT
http://www.contentwithstyle.co.uk/Articles/44/processing-the-output-buffer-with-xslt/

Opitz, Pascal
Content With Style
2005

Abstract:

This article shows an example of a technique mentioned in one of our recent articles. It uses the PHP output buffer in combination with XML as intermediate application layer. Ideally you should familiarize yourself with this concept first.