Thread:Project:Support desk/Unable to upload files to the server using Special:Upload/reply (4)

Imagine your wgServer is http//www.example.com, but your web server is actually at http://example.com and the server enforces it by redirecting all requests to http//www.example.com to http//example.com. Then when you submit a form in your MediaWiki, it posts the data to http//www.example.com, but before it reaches the PHP engine, the web server intercepts the requests and redirects it to http//example.com, losing the posted data, so MediaWiki receives the request as if nothing has been submitted. If you enable debugging on MediaWiki you won't see any POST request.