Does anybody know a solution to upload files using drag&drop within a php
based website?
As far as I know, it's not actually possible to handle drag & drop of external objects within the web browser at all. Drag & drop actions are functions of the operating system and web browser, and since both are client-side, they have nothing to do with PHP - and even less with database functions - so it's pretty far outside the scope of this list. But if there is a way to handle it, it will be done using JavaScript's event handling functions.
Morgan