[RFC] Default expression

Hi gang, New RFC just dropped: https://wiki.php.net/rfc/default_expression. I think some of you might enjoy this one. Hit me with any feedback. This one already comes complete with working implementation that I've been cooking for a little while. Considering I don't know C or PHP internals, one might think implementing this feature would be prohibitively difficult, but considering the amount of help and guidance I received from Ilija, Bob and others, it would be truer to say it would have been more difficult to fail! Huge thanks to them. Cheers, Bilge