Are we sure about this? It seems like the "right" way to implement drag-and-drop sort of functionality is through a Java applet that talks to PHP. (I know Java has some d-n-d vocabulary built in, so I would imagine it wouldn't be terribly hard to write that applet.)
To clarfiy, I'm thinking about d-n-d like "drag the photo to upload here -> <-" and you could drag a file from your desktop to the target (inside a browser window). I imagine that would trigger results being posted to a PHP page.
best,
Eric