Virtual directories are not real folders.

For the record here, run to list them:

%windir%\system32\inetsrv\appcmd list vdirs  

I agree virtual directory is not a real folder.
But the target is always a physical folder. Logically, php should play with the target physical folder when a virtual directory is referred to.

There is no symlink or directory created, so there is no way for PHP or any other application to know them without calling the IIS API functions. ASP.net has PhysicalApplicationPath or ApplicationPath (along other), FCGI only knows about the physical path. It would be very slow and inefficient if we would have to manually resolve these paths on each request or file operation (from a php script for example).

Thanks for the explanation.
You are right that it would be a slower process.

Right now I am handling this by having the physical path as a defined variable and using it all over the file system functions.

But it would be better if php could check with fcgi whether it's a virtual directory if the physical folder is not present. This will come handy when a user chooses to move a folder to a remote location. Then there won't be any need to modify the codes.