PHP 7 is in itself a major optimization. A good part of PHP's code base was rewritten for this release and most official benchmarks show that, generally speaking, almost any PHP code will run about two times faster or more with PHP 7 than with previous versions.
PHP is programmed in C and optimizing the performance of Zend's Ahead-Of-Time (AOT) compiler depends ultimately on using the C compiler's internal logic in an optimized way. This latest version of PHP is the result of many years of research and experiments by Zend. The greater part of these optimizations was implemented by eliminating the performance overhead generated by certain PHP internal structural constructs and data structures. According to Dmitry Stogov[1] ...
