I remember reading on some of Symfony’s web sites that Zend Framework was only a library and not a framework.
What makes frameworks special? Wiki states:
I think these four can be rephrased into one: with enforcing a particular program flow, a framework offers a ready-to-use code base to address typical tasks, for example web apps.
There are also some side-effects of being a framework, such as:
is a framework for functional and procedural programming in PHP that I created to follow up on some of my ideas and illustrate them
Functional PHP
Testing static dependencies
Dependencies management without OOP
The following resources are available: