Kohana is a lightweight, open-source framework created to build web applications. Based on Code Igniter, Kohana employs strict PHP5 conventions for OOP (Object-Oriented Programming) and true auto loading. Its HMVC (Hierarchical Model-View-Controller) architecture allows for a hierarchy of cascading directory structures that let developers override properties, methods, and files higher up in the application stack, while maintaining each directory’s autonomy. In addition, Kohana offers powerful event handling, multiple session drivers, simple database abstraction using SQL helpers, and libraries that transparently handle external APIs. Its generous BSD license lets developers use and modify the framework to build commercial applications.