I never got a reply to the other question I asked here about DBG clienthost not working, so I downloaded the source to have a look.

I can see the source attempts to find the clienthost from HTTP_SERVER_VARS. Unfortunately, in the PHP scripts I am running (under standard Apache, on CentOS5), there is no such variable. No wonder DBG doesn't work.

Anyone have a clue why?

In CentOS 5, by default, register_long_arrays is set to Off. This removes the HTTP_SERVER_VARS variable, thus breaking DBG.
Setting
register_long_arrays On
in php.ini makes it start working again.

probably you're talking about FREE version of debugger (2.x)
As of version 3.x, DBG works perfectly well regardless if long arrays are defined or not.

Thanks, dmitri, yes I am talking about the free version.

Glad to hear this is fixed in the next version (which will presumably become free one day?).

Hopefully my question and solution will help someone else, anyway.