Editing Zend Engine (section)

== Architecture ==
Zend Engine is used internally by PHP as a compiler and runtime engine. 
PHP Scripts are loaded into memory and compiled into Zend [[opcodes]]. 
These opcodes are executed and the HTML generated is sent to the client.<ref>{{cite web|url=http://www.careerride.com/PHP-zend-engine.aspx|title=PHP - What is zend engine?|publisher=careerride}}</ref>

To implement a Web script interpreter requires three parts:
# The interpreter part analyzes the input code, translates it, and executes it.
# The functionality part implements the functionality of the language (its functions, etc.).
# The interface part talks to the Web server, etc.
Zend takes part 1 completely and a bit of part 2; PHP takes parts 2 and 3.

Zend itself really forms only the language core, implementing PHP at its very basics with some predefined functions.