Undine is a UI Engine, written in PHP.
It allows the fast creation of complex web-based User Interfaces and so it is mainly aimed at Rapid Prototyping and Rapid Application Development.
An application created with Undine is normally just a simple description of the structure of the UI in a pretty simple XML format that is then dynamically read by the Undine run-time. The engine is also able to read the schema's metadata directly from the DB itself, so there is no need to explicitly declare the data structures used by the application itself. While this takes care of the biggest part of the application, it is still possible to extend the default behavior provided by the engine with additional PHP functions and methods that can be hooked up to the standard flow of the engine's objects.