I'm searching for a PHP syntax highlighting engine that can be customized (i.e. I can provide my own tokenizers for new languages) and that can handle several languages simultaneously (i.e. on the same output page). This engine has to work well together with CSS classes, i.e. it should format the output by inserting <span> elements that are adorned with class attributes. Bonus points for an extensible schema.
I do not search for a client-side syntax highlighting script (JavaScript).
So far, I'm stuck with GeSHi. Unfortunately, GeSHi fails abysmally for several reasons. The main reason is that the different language files define completely different, inconsistent styles. I've worked hours trying to refactor the different language definitions down to a common denominator but since most definition files are in themselves quite bad, I'd finally like to switch.
Ideally, I'd like to have an API similar to CodeRay, Pygments or the JavaScript dp.SyntaxHighlighter.
Clarification:
I'm looking for a code highlighting software written in PHP, not for PHP (since I need to use it from inside PHP).