Even with PHP7, PHP still feels like it is playing catch up. There is nothing new or revolutionary in PHP7, just adopting features present in other major languages. Adopting as other newer languages like Go and Rust seems to be moving beyond those features. A catch up into a world that's on its way out, if one will feel so blunt. PHP's raison d'être remains its ease of getting an instance running on a webserver. But…
Well, Rust is playing catch up with the "change code and run" speed of PHP.
It's just a weird comparison. PHP is competitive with JS, Python, Ruby and even Java. But Rust? That's C/C++/D territory. And Go is somewhere in between.