PHP is just another tool. If we're talking about backend, then its perfomance is good enough for small to middle sized applications. PHP borrowed a lot of language features from other languages in the last decade, it's a different language now, still there is a lot of old poor written code.

PHP 7 is great for those who are already used PHP for years, cause it uses half of CPU resources doing the same tasks as PHP 5.6. I don't think there is any good reason switching from Golang for example if you are aiming for writing scalable applications; still, every experienced PHP dev I know are still getting their things done and doesn't consider switching.