As explained on the Why another PHP framework? page, I was inspired to write PHOCOA after writing several applications for Mac OS X using Apple's Cocoa Framework.
Now of course PHP is very different from Objective-C, and web apps are very different from desktop apps, but it's the basic concepts that we've carried over into PHOCOA, and in many times improved for PHP or web use.
Know Cocoa and want to know what PHOCOA does? Know PHP and want to learn more about the Cocoa concepts used in PHOCOA?