Maybe you’ve already heard these days about actual refactoring of php 5.5 engine by Zend team.
Even if php is the world leading language for development, more and more serious players are emerging like Facebook with its HHVM.
To stay the longer in the run, it is mandatory to go further than a simple syntax release, it is important to improve performance.
If typical real-life PHP application spends about 20% of the CPU time in memory manager, 10% in hash tables operations, 30% in internal functions and only 30% in VM, the team decided to focuse on memory representation of many data types that won’t impact the all language structure.
That improved some applications performance from 10% to 30%, check this link https://wiki.php.net/phpng.
If tests have shown 20% of improvement for CMS like WordPress (v3.6), 11.7% for Drupal (v6.1), published results concern old cms versions, and like Dmitry Stogov (Mr Performance inside Zend family) said, gain in performances will strongly depend of your application.
So, we are very excited about improvements in php and we’re waiting impatiently, but, this refactoring is only a contribution and we don’t have yet the certitude it will be finally part of php.
The refactoring is still in progress but is enough advanced to test it locally on your machine.
Depending on the framework or cms you work with, you will gain in performance or not.
One advice, just wait.