This page is a resource listing current, actively maintained PHP frameworks. If you are looking for more general information about the different types of PHP frameworks available, then you should look at PHP The Right Way: Frameworks.
You can see a more complete list - including more historical entries - on the two websites below:
An optional rule is that any framework part of the PHP-FIG will automatically be put onto the list.
We will police this list now and then to make sure new listings meet the requirements, and to make sure projects have not expired. If a project gets marked as inactive then we'll remove it.