In reply to:

[If] PHP released a new version under GPLv3 only (not likely as it'd be a bureaucratic nightmare if many people had contributed to PHP)...


I doubt it'd be a "bureaucratic nightmare" if the contributors donated their code with the standard boilerplate text that allows licensees to choose GNU GPL v2 or any later version, at their choice.
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Toby Speight
030103016 (80GB Mk2a, blue)
030102806 (0GB Mk2a, blue)