There’s a much more detailed chapter about this subject in my book Principles of PHP Package Design.

These days, good PHP object-oriented libraries are all around and easily available. To me, it is actually thrilling to be part of this flourishing community, while working with Symfony2 and blogging about the Framework, the Components and their neighbors (like Silex). It seems like everything is made for contributing to this nice and friendly environment, with tools like GitHub (online collaboration), Composer (dependency management), Packagist (package archive) and Travis CI (continuous integration).