I am writing a web based game in Actionscript 3, and this game connects to PHP scripts to deal with the online functionality and database connectivity needed.

I am interested in purchasing NuSphere PHPED because of its debugger, since the game's PHP scripts will be quite complex and debugging "blind" can prove to be pretty time consuming.

The example screencast just showed how to debug a simple dynamic webpage, so I am unsure if the debugger can handle something like this as well?

Is it possible to debug a script called from a AS3 program on a webpage? And, if so, how does this work?

I have worked with
Flex Builder 3 and Flash Builder 4
Charles proxy
PHPEd

It is possible to debug (AS3) flex application
see what gets passed in the middle with Charles
and debug PHP with PHPEd

This is probably the best debugger and the easiest to setup.

I did try Zend and XDebug as well but never got them working.

Flex and Charles are not required to test the PHP script.

All you have to do is setup the debugger and make sure the debug cookie is set before you make the php script call you wish to debug.

There is a debugger Firefox extension, or you can use the Edit Cookies one and set the cookie yourself.[/list]

Yes, you can debug ANY PHP script, just add a DEBUGSESSION param to script call.
I would write a "debug-additiv" and set it to either debug string or empty, depending of dev/prod version of your AS3 script.