FWIW: It could be done with ereg, but you don't wanna go there. It would probably look something like:
eregi_replace("<select[[:space:]]([e]|e([n]|n([a]|a([b]|b([l]|l([e]|e[d])))))))"...
I'm not sure that would work, but that's okay, because it's so nasty I'd never use it!