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. In October 2006, after ten months of development, the first alpha version of Yii was released, followed by the formal 1.00 release in December 2008.
Yii 1.1 was released in January 2010 adding a form builder, relational Active record queries, a unit testing framework and more. The Yii community continues to follow the 1.1 branch with PHP7+ support and security fixes. The latest version 1.1.23 was released in December 2020.
In May 2011 the developers decided to use new PHP versions and fix architectural shortcomings, resulting in version 2.0.[3] In May 2013 the Yii 2.0 code went public, followed by the first stable release in October 2014. PHP8 is supported since version 2.0.38.[4] The latest version 2.0.51 was released in July 2024.[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.