This is one of the "loopholes" that RMS was talking about closing recently

And of course that won't apply retrospectively to people like you who have already received PHP under GPLv2. It'd only be a problem if RMS changed the conditions in GPLv3, and PHP released a new version under GPLv3 only (not likely as it'd be a bureaucratic nightmare if many people had contributed to PHP), and you wanted to upgrade to that version.

Peter