If you're thinking of trying your hand at creating your own PHP framework, you might want to check out this post from Matrin Rusev about some of the lessons he learned (the hard way) about framework construction.

After using Codeigniter, CakePHP and Zend Framework for a while I decided to build my own framework. I wanted to include some features that I couldn’t find the way I like them in none of the projects I tested. These are some lessons I learned the hard way. I hope you’d find some useful tips for your software projects.

The post looks a a few different topics - doing good planning before development starts, using third-party libraries, planning out the syntax the components inside of your framework will use, how to handle debugging and two tools you can use to benchmark the end result.