Yii is an open source, object-oriented, component-based MVC PHP web application framework.


Yii features include:

1) Model-View-Controller (MVC) design pattern.
2) Generation of complex WSDL service specifications and management of Web service request handling.
3) Internationalization and localization (I18N and L10N). It supports message translation, date and time formatting, number formatting, and interface localization.
4) Layered caching scheme. It supports data caching, page caching, fragment caching and dynamic content. The storage medium of caching can be changed.
5) Error handling and logging. Errors are handled and presented more nicely, and log messages can be categorized, filtered and routed to different destinations.
6) Security measures include cross-site scripting (XSS) prevention, cross-site request forgery (CSRF) prevention, cookie tampering prevention, etc.
7) Unit and functionality testing based on PHPUnit and Selenium.
8) Automatic code generation for the skeleton application, CRUD applications, etc.
9) Code generated by Yii components and command line tools complies to the XHTML standard.
10) Carefully designed to work well with third-party code. For example, it’s possible to use code from PEAR or Zend Framework in a Yii application.


he Yii project has an extension repository consisting of user-contributed components. There was also an official extension library, zii, which was then merged with the core framework. It is bundled in every release since Yii version 1.1.0, and it includes additional behaviors and widgets, such as grids and jQuery UI.


Yii comes with a collection of official documentation, such as a tutorial to develop a simple blog application, a guide that gives the description of every feature and a class reference which gives every detail about properties, methods and events. There's also a user-contributed documentation, most of which is available within the wiki on the official website.


Yii is released under the New BSD License (3-clause license). This means that it's possible to use it for free to develop either open-source or proprietary Web applications. The text contained in the Official Yii Documentation is licensed to the public under the GNU Free Documentation License (GFDL). In general, the Yii documentation content can be copied, modified, and redistributed so long as the new version grants the same freedoms to others and acknowledges the authors of the Yii documentation article used.