WHAT IS YII?
Yii is an open source, object-oriented, component-based MVC PHP web application framework.
WHAT IS YII BEST USED FOR?
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.
companies Which use Yii including PokerTube, Utrip, and FreshMail.
REASONS TO USE YII:
Fast: Yii gives you the maximum functionality by adding the least possible overhead
Efficient: Write more code in less time with simple, yet powerful APIs and code generation
Secure:Sane defaults and built-in tools helps you write solid and secure code
Yii currently has two major versions available: 1.1 and 2.0. Version 1.1 is the old generation and is now in maintenance mode. Version 2.0 is a complete rewrite of Yii, adopting the latest technologies and protocols, including Composer, PSR, namespaces, traits, and so forth. Version 2.0 represents the current generation of the framework and will receive the main development efforts over the next few years. This guide is mainly about version 2.0.
REQUIREMENTS AND PREREQUISITES:
Yii 2.0 requires PHP 5.4.0 or above and runs best with the latest version of PHP 7. You can find more detailed requirements for individual features by running the requirement checker included in every Yii release.