Yii 2 is the latest version of the Yii framework - a high-performance, component-based PHP framework
Yii is a generic Web programming framework, meaning that it can be used for developing all kinds of Web applications using PHP. Because of its component-based architecture and sophisticated caching support, it is especially suitable for developing large-scale applications such as portals, forums, content management systems (CMS), e-commerce projects, RESTful Web services, and so on.
Yii 2.0 is the current version of the Yii PHP framework, released on October 12, 2014. The latest version can be downloaded from the Yii website. Guidelines on how to upgrade minor Yii 2.0 version and changelog can be found here.
Yii 2.0 is a complete rewrite of Yii 1.1 based on PHP 5.4 improvements and aims for simplicity, performance and extensibility. The framework adopts php namespaces and traits, PSR standards, composer, and bower. Yii 2.0 implements the dependency injection container and service locator. It makes the applications built with Yii more customizable and testable.
Official documentation can be found in the Definitive Guide to Yii 2.0. Further important documentation sources:
More information on the current project status can be found in the Yii 2.0 release announcement and the project roadmap.
