Lukas Smith has put together a recent post to his blog with some thoughts on standardization of interfaces in PHP applications to help improve code quality and interoperability.

In my previous blog post I was brainstorming the possibility of collaboration between various frameworks to define a set of common interfaces. But I kind of failed to explain why this would be useful. Herman's "rebuttal" made this omission on my part quite clear. [...] That being said the open questions left in my previous blog might still prevent this idea to take off, even if I manage to convince the general community that the above mentioned negative effects are not such a significant concern.

He talks first about some of the things he sees PHP as having done right (citing its popularity) and contrasts it to Java based on the standards they impose. He goes on to mention how interfaces, introduced early enough in the process, can help with the "best tool for the job" idea (with an example involving Symfony2, Zend Framework and Doctrine).