A new microframework for PHP has been announced - Tekuna - and coming in at just over 3000 lines, makes it one of the smallest out there. From the Tekuna website:

Tekuna is a compact framework for web-based applications. It provides a stable basis and a generic infrastructure for your projects. Tekuna has a very small footprint and will not pollute your codebase with unnecessary stuff.

Among the list of current functionality are things like:

• friendly URI handling
• MVC structure
• input filtering
• full UTF-8 support
• fully unit tested code
• E_STRICT compliant

You can find out more from the framework's website including links to their documentation, quickstart and latest download.