PHP 4.0 and Zend Engine

A pair of Israeli programmers, Zeev Suraski and Andi Gutmans, completely rewrote the interpreter used in PHP and created version PHP 4.0.

PHP 4.0 is based on an open source scripting engine called Zend Engine. The name Zend is a composite of its creators’ names Zeev and Andi. The Zend Engine is written as a highly optimized and powerful backend that can also be used outside PHP applications.