Gubed PHP Debugger is a visual debugger for PHP. This means that it will help you follow the flow of execution in your scripts to find logical errors or understand why the script behaves in certain ways.
Gubed consists of many parts that work in symbiosis to bring you a working debugger environment. Those parts are
The Server Scripts
The Client
The Proxy
There are also things that you need that are not part of Gubed
A PHP enabled web server
A web browser