It got a proper, rewritten, parser.
It got a free-double-the-speed update for almost all working code in version 7.
It got a full featured package manager (composer).
It got many next-generation frameworks and libs that don't fall prey to the issues that plagued early PHP codebases.
It got the "share nothing" model correctly from the beginning.
It's still the easiest and cheapest to deploy, and has tons of extensions for everything.
There's active work for a JIT and async (a la Node/Tornado etc) hooks.