[calvin]

I'm having exactly the same problem, same system (Ubuntu Karmic Koala). Prerequisites installed, XHP module installed, it's listed in my phpinfo. For any XHTML tag I include (a, span, ...) the error message says class not included:

  Fatal error: Class 'xhp_span' not found in ...

Any ideas on how to fix would be appreciated. Google and Bing have nothing so far and the module configuration info on the GitHub page is limited: http://wiki.github.com/facebook/xhp/

[chaosmachine]

So, it seems you need to include init.php. Not sure why that doesn't happen automatically.

http://github.com/facebook/xhp/issues#issue/2