Phergie is not a traditional framework, more of a modular application with many libraries that you can combine to bring different features into an IRC bot. It's used to build IRC daemons in the same way that web frameworks are used to build web applications. Features (Plugins) are their own separate libraries so that the builder/author may customize the bot to their specific needs.
Under the hood Phergie is built on top of ReactPHP (represented here by Cees-Jan Kiewiet who is also a valued contributor to Phergie). Phergie has a long history of keeping up with best practices as well as keeping up with the advancement of Async PHP changes (Thanks to ReactPHP).