PHP and Zend Engine

What is Zend Engine ?

The Zend Engine has been the core scripting engine of PHP since PHP version 4

The Zend engine is a set of components that make PHP what it is. The most important Zend engine component is the Zend Virtual Machine, which is composed of the Zend Compiler and the Zend Executor components. We could also add the OPCache zend extension in such category. Those three components are the heart of PHP (or the brain, you choose), they are critical and they are the most complex parts of all the PHP source code. In the current chapter, we’ll try to open them and detail them.

Zend's History with PHP

Zend's contribution to PHP began in 1997 when Zeev Suraski and Andi Gutmans started work on a rewrite of the core scripting engine of PHP. This work helped to redefine PHP as a full-featured development language.

Zend's contributions continued with PHP 4 which saw the introduction of the Zend Engine, a highly optimized execution engine. This enhancement allowed modules such as debuggers, performance boosters and custom loaders to dynamically extend PHP for a broader range of functionality. Whenever you're using any plug-in module today, you're doing so thanks to the extensibility support of the Zend Engine. In addition, the Zend Engine provides memory and resource management, and other standard services for the PHP language. Zend continued its work on PHP and Zend engine with the introduction of Zend Engine 2. Zend Engine 2 debuted in PHP 5.0 and added a robust and extensible object model and even more performance enhancements.

In PHP extensions are known to be "Zend extentions" and modules are known to be "PHP modules.

In traditional life, we talk about “PHP extensions” versus “Zend extensions”.
The thing that differentiate them is the way they are loaded :

• PHP extensions (aka PHP “modules”) are loaded in INI files as a “extension=pib.so” line
• Zend extensions are loaded in INI files as a “zend_extension=pib.so” line

First of all, Zend extensions are compiled and loaded the same way as PHP extensions.

Sources:
- www.zend.com
- www.phpinternalsbook.com