It is generally convenient that the GLOBALS superglobal is expanded together with local varables, but this leaves no way of distinguishing the two. How about also showing GLOBALS as an expandable tree node in the variable list?

It also looks like globals added by assigning directly to $GLOBALS never get displayed.

This may be an upstream issue with Xdebug itself. Currently, I'm merging the the variables of the two different "contexts" (which are only Superglobals and Locals, according to the result) that are returned:

2009-07-21 23:05:34.309 MacGDBp[59263:10b] --> context_names -d 0
2009-07-21 23:05:34.310 MacGDBp[59263:10b] <-- <?xml version="1.0" encoding="iso-8859-1"?><response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="http://xdebug.org/dbgp/xdebug" command="context_names" transaction_id="macgdbp"><context name="Locals" id="0"></context><context name="Superglobals" id="1"></context></response>

The Superglobals context only holds the _POST/_GET/_COOKIE arrays and Locals holds everything else, which means I can't really do anything about this unless Xdebug changes.