Whenever you start a new project and make yourself a mind on how to integrate libraries, develop components etc. while you want to consider some third-party libraries or frameworks (or even you think about to develop your own framework), you should know about the PHP Standards Working Group.
The group offers proposals developers can follow as a lowest common denominator to make their development inter-operable with code from libraries or frameworks like Zend Framework, Symfony, PEAR, Lithium, CakePHP, Yahoo!, SolarPHP, Doctrine, PHP Core, Agavi, Typo3, Flow3 and many others.
This can definitely save some headaches. Thanks for the initiative! SPL Autoload reloaded :). And Namespaces.