What is Zend?
Zend is an open source scripting engine developed by company named Zend that wrote PHP as well.
The Zend scripting engine provides a modular architecture, and can also be used in applications outside of PHP.
It is a well known engine for developing web sites that requires performance, reliability and extensibility.
Zend services are provided through several separate engines like Zend Studio, Zend Guard, Zend Optimizer.
Zend Studio with it's latest version edition 5.5 is the only Integrated Development Environment (IDE) available for professional developers.
Through a comprehensive set of editing, debugging, analysis, optimization and database tools, Zend Studio 5.5 speeds development cycles and simplifies complex projects.
Zend Guard, at first known as Zend Encoder, protects your commercial PHP 4 and PHP 5 applications from reverse engineering ie. no one is able to use nor alter the code that has been written using Zend and protecting with Zend Guard, unauthorized customization won't be allowed and unlicensed use and redistribution also are permitted using this Zend package.
Zend Optimizer as is one of the most popular PHP plugins for performance improvement and the replacement code blocks perform exactly the same operations as the original php code, only faster.