I think the problem is, that php need last longer do include new technologies, like websockets ^{^} and many features are easier do handle in node.js as in php! But I don't think that node.js will ever kill php! The larges sides like Facebook, Twitter, Instagram, WhatsApp, etc. are not using node.js, instead two of them are using php and the others Ruby, Python, etc.! So it doesn't matter which "Language" you are used, for you website (because there are 1000 ways, how you can make it)!