Changes

The combination of PHP 3 and Apache quickly lead to the widespread adoption of PHP, and it is commonly estimated that, at its peak adoption level, PHP3 was used to power over 10% of all web sites on the internet.

With PHP 4 Andi Gutmans and Zeev Suraski once again re-architected PHP from the ground up. PHP 4 was built upon a piece of technology called the Zend Engine. The move to the Zend Engine brought about a number of key improvements in PHP: