PHP debug / Trace

desperately need a debug tool that works like the xcart webmaster mode tool (basically an element inspector similar to firebug where you hover over an element (eg a price in the shopping cart) and a popup shows you which language file, variable, or template file you need to edit.)

Eg when trying to change virtuemart layouts, you end up having to muddle through the code manually to trace what's coming from where, and doing full text searches of entire component folders to find the elements you wish to edit, because firebug can only see the rendered html, not the php that built it.

Firebug is fine for html/css but when it comes to things like virtuemart, you're working in the dark unless you've got good experience with PHP IDEs (which most joomla designers don't have).