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

Yii is pronounced as "Yee" or [ji:] and in Chinese it means "simple and evolutionary" and it can be an acronym for "Yes It Is!".

[2] Yii started as an attempt to fix perceived drawbacks of the PRADO framework: Slow handling of complex pages, steep learning curve and difficulty to customize many controls.

Yii 1.1 was released in January 2010 adding a form builder, relational Active record queries, a unit testing framework and more.

[5] The Yii project includes a repository of user-contributed extensions in addition to an official extension library, zii, which was merged with the core framework;[8] it has been bundled in every release since Yii version 1.1.0 and includes additional widgets such as grids and jQuery UI.