Are you limited to PHP?
No, but further: the question (about being "limited") presupposes something that isn't true.
If you're doing PHP here, you're doing it wrong—unless the PHP application is written with great care (i.e. unidiomatically) and has some way to reveal its own program text (as first-class content). Otherwise, that's a complete failure to avoid the "elsewhere"-ness that we're trying to eradicate.
