PHLY is a library of PHP classes designed with the following intentions:

* Loosely coupled; dependencies should be few, and no base class should be
  necessary.
* Extendible; all classes should be easily extendible. This may be via
  observers, interfaces, adapters, etc.. The base class should solve 80% of
  usage, and allow extensions to the class to fill in the remainder.
* Designed for PHP5 and up; all classes should make use of PHP5's features.
* Documented; all classes should minimally have excellent API-level
  documentation, with use cases in the class docblock.
* Tested; all classes should have unit tests accompanying them.
* Open source and commercial friendly; all classes should use a
  commercial-friendly open source license. The BSD license is one such example

For more information, see http://weierophinney.net/phly/