XPath and SimpleXML aren't fast or easy enough?

php.net/domxpath
php.net/simplexml

Unless and until libxml2 supports the selectors API directly, I don't
think there's much point trying to handle this in PHP. At any rate, it
should be possible to create a userland library that parses CSS
selectors and turns them into XPath calls: in fact, I believe this is
what phpQuery does already.

This could be reopened if libxml2 implements support for the API, but
for now, I think this is best closed Won't Fix in favour of this being
better suited to a userland solution.