Zend Framework requires a PHP 5 interpreter with a web server configured to handle PHP scripts correctly. Some features require additional extensions or web server features; in most cases the framework can be used without them, although performance may suffer or ancillary features may not be fully functional. An example of such a dependency is mod_rewrite in an Apache environment, which can be used to implement "pretty URL's" like "http://www.example.com/user/edit". If mod_rewrite is not enabled, Zend Framework can be configured to support URL's such as "http://www.example.com?controller=user&action=edit". Pretty URL's may be used to shorten URL's for textual representation or search engine optimization (SEO), but they do not directly affect the functionality of the application. Zend recommends the most current release of PHP for critical security and performance enhancements, and currently supports PHP 5.2.11 or later. Zend Framework has an extensive collection of unit tests, which you can run using PHPUnit 3.4.15 or later. You will find a table listing all extensions typically found in PHP and how they are used in Zend Framework below. You should verify that the extensions on which Zend Framework components you'll be using in your application are available in your PHP environments. Many applications will not require every extension listed below. A dependency of type "hard" indicates that the components or classes cannot function properly if the respective extension is not available, while a dependency of type "soft" indicates that the component may use the extension if it is available but will function properly if it is not. Many components will automatically use certain extensions if they are available to optimize performance but will execute code with similar functionality in the component itself if the extensions are unavailable. Below is a table that lists all available Zend Framework Components and which PHP extension they need. This can help guide you to know which extensions are required for your application. Not all extensions used by Zend Framework are required for every application. A dependency of type "hard" indicates that the components or classes cannot function properly if the respective extension is not available, while a dependency of type "soft" indicates that the component may use the extension if it is available but will function properly if it is not. Many components will automatically use certain extensions if they are available to optimize performance but will execute code with similar functionality in the component itself if the extensions are unavailable. Below you can find a table listing Zend Framework Components and their dependencies to other Zend Framework Components. This can help you if you need to have only single components instead of the complete Zend Framework. A dependency of type "hard" indicates that the components or classes cannot function properly if the respective dependent component is not available, while a dependency of type "soft" indicates that the component may need the dependent component in special situations or with special adapters. At last a dependency of type "fix" indicated that these components or classes are in any case used by subcomponents, and a dependency of type "sub" indicates that these components can be used by subcomponents in special situations or with special adapters. Even if it's possible to separate single components for usage from the complete Zend Framework you should keep in mind that this can lead to problems when files are missed or components are used dynamically.