I agree that performance-wise, PHP has become a lot better than what it was before. Still, it has huge inconsistencies in it's language structure. By the way, Facebook tried to go with PHP but they later had to write their own language called Hack, which is basically PHP on steroid (they modified the compiler itself). So, it proves that PHP doesn't scale up that well. That being said, I am by no means a PHP hater. It has been my bread and butter for years! My OP was rather about the fact that PHP.net isn't good when it comes to social media handling LOL.
Edit: Backwards compatibility is a lame excuse. If backwards compatibility is an issue, why not come up with a completely new version like let's say PHP 10 and make everything good there (while continuing to support the current versions and development)? A similar approach was taken by AngularJS and I don't see why PHP can't do it.