Warning: Tested with Sablotron 0.8.2 and php 4.1.1. Don't think that older Sablotrons have been the same ... NOTE: Have to recompile Sablotron to get encoding support I think.
See XSLT Functions and click through all the functions. Avoid some tutoriels on the Web on XSLT with PHP/Sablorton that deal with older versions (or fix them :)
Of course one could do fancier things that just associate 2 files. E.g. not wrap the result into <html> but fragments of html and do some LEGO.