Some Information on A Help Database Application Using PHP and XML

Et al, I'm interested in either designing or participating in a current project which utilizes PHP and XML to create a documentation application. My company (caravelcms.org) has designed a content management system using PHP and we are currently investigating how we can document effectively our various userland functions. Instead of re-inventing the wheel, I thought I'd put a call out to the PHP community to see if you could push me in the right direction. Basically, what I want is a way of writing and storing and inter-linking documentation for our application. It seems XML would be the best route to go, but I'd prefer the documentation app to also be in PHP. I'd imagine others have had a similar desire and perhaps an app is out there already. If anyone has insite, please let me know. Sincerely, Peter John Hartman caravelcms.org