VS.Php Standalone Edition 2.3

Powerful PHP IDE and PHP editor with built-in HTML, CSS and JavaScript editor

Free

Dev-PHP 3.0 is an editior for php scripts with integraed debugging functions.

Rapid PHP editor is a faster and more powerful PHP editor.

This is a PHP IDE that can be installed as an addon for Visual Studio 2013.

Free

Gubed PHP Debugger is, as the name suggests, a program to debug PHP scripts.