Phalcon is an open source, MVC based PHP framework. Apart from promoting MVC architecture, they offers you a lot of in-built features for faster web development such as ORM (Object Relational Mapping),Templating Engine (Volt),Events Management, Encryption, caching, Validation/Escaping/Filters etc.
Yii is a very high performance PHP framework used for development of web applications. It’s free and open-source framework which follows MVC architecture.So now you might be thinking that there is many other PHP MVC framework like Laravel, Symfony, Cake, Codeigniter etc. are available why i use yii framework.The best thing about Yii’s is it’s performance. Definitely If you are making highly-scalable web application then you can’t ignore this point.