On the O'Reilly PHP blog (ONLamp.com), there's a new post by Michael Ross with an overview of the popular PHP IDE from Zend, their Zend Studio for Eclipse:

Zend Studio for Eclipse is the company's latest update of its PHP IDE, and carries a version number of 6.0. As a foundation, it uses Eclipse, an extensible open source platform for software development that is growing in functionality and widespread usage every year. It also utilizes the PHP Development Tools (PDT) framework.

He looks at the product from all sides - the releases of the products, requirements, pricing, installation and an overview of the interface (complete with screenshots). He also mentions other features that come bundled with the editor like testing integration, file/version management and a built in debugger (as well as special support for the Zend Framework).