From the ‘Still Waiting for PHP 6’ files:
Three and a half years ago in December of 2011, I wrote about Facebook’s new HipHop Virtual 
machine for improving PHP. Now it looks like mainline PHP developers are going to soon go the same route.
The Hip Hop Virtual Machine (hhvm) makes PHP faster by providing Just-In-Time (JIT) compilation and it’s now something being baked into the PHP next gen branch.
“When we aren’t looking for pictures of kittens on the internet, internals developers are nearly always looking for ways to improve PHP, a few developers have a focus on performance,” a post on PHP.net states. “By making these improvements, the phpng branch gives us a considerable performance gain in real world applications, for example a 20 percent increase in throughput for WordPress.”
This is a great idea of PHP which has been evolving really nicely over the last two years. The PHP 5.5 release for example got the Zend Optimizer+ Opcode cache system, which I personally see a huge improvement from for running PHP applications.
PHP 5.6 is currently at its Beta 3 stage and is already feature frozen, so I wouldn’t expect the next gen branch stuff to land until a future PHP 5.7 (or PHP 6?!)
Sean Michael Kerner is a senior editor at InternetNews.com. Follow him on Twitter @TechJournalist