Languages evolve and PHP did it and still does. PHP is as old as Java. Haskell is even older. In the category of PHP, Java and Haskell we pretty much rehash the same language features with some minor twists in new languages. Hardly we get new features that make an impacts like in the case of Go's goroutines or Rust's borrow checker.

The problem is the runtime of the language, on which PHP, the language, runs. That could be easily improved on porting the language to a VM like Facebook did with Hack or to something like GraalVM. Runtimes over languages.

There are 55k openings on Indeed for React jobs and 8k PHP jobs. When the absolute numbers are lower, there's more opportunity for high percentage growth, which is what they used to rank them.