The Zend Optimizer goes over the intermediate code generated by the standard Zend run-time compiler and optimizes it for faster execution. In addition, the Zend Optimizer enables PHP to load and execute files encoded by using Zend Guard.

The standard Zend run-time compiler used by PHP is indeed extremely fast, generating code that is usually 2 to 10 times faster. But an application that uses the Zend Optimizer typically executes another 40% to 100% faster.

The current version of the Zend Optimizer works with PHP versions 4.2.x through version 4.4.x and versions 5.0.x, 5.1.x that are compiled without debug support (the default configuration of the standard PHP package). OS X Mac supports PHP versions: 4.3.x through 5.1.x.

In addition, Zend Optimizer will not run if the following PHP settings are enabled:

* Thread Safety
* Enable Versioning

Files encoded with the Zend Guard must be compiled with a compatible version of Zend Guard. When in doubt always use the latest version of Zend Optimizer. If the versions of Zend Guard and Zend Optimizer are incompatible, the Optimizer will fail to run encoded files and will register an error message.

How the Zend Optimizer installed in Windows?

To install the Zend Optimizer under Windows

1. To ensure that your PHP installation is compatible with the Zend Optimizer, it is recommended to use the Windows packages posted in the Zend Store which are compiled in non-debug mode The Zend Optimizer works only with non-debug PHP binaries.
2. The Zend Optimizer for Windows package is a self-extracting installer. Simply run the package file, and follow the installation instructions.
3. If you are running a server module (e.g.ISAPI), restart your server. For Microsoft IIS, run net stop iisadmin, and then net start w3svc, from a command line console.