A well designed framework should allow you to use its separate components as well as the whole thing. For example, you can use Zend Framework as a full framewor

A well designed framework should allow you to use its separate components as well as the whole thing. For example, you can use Zend Framework as a full framework, or as a library by importing individual classes (e.g. I use Zend_Http_Client for connecting to RESTful APIs, even though none of my projects use Zend as a framework). Unfortunately most of the other frameworks I've used tend to be all or nothing.