Manual:$wgUploadPath

Details
The relative path to the upload directory.

This is used to construct the URLs for viewing uploaded files.

In most cases this is just the path component, such as "/w/images".

If uploaded files are served from a different domain, this can be a fully-qualified URL with hostname, such as "http://upload.wikimedia.org/wikipedia/en".

If the variable contains a local path (without "http://") then it must start with a slash, otherwise it will result in a bad URL.

(For example if you set it to "foldername" it will result in files being loaded from " http://www.example.comfoldername " - note the missing slash after ".com")

To enable permission checks on image files, $wgUploadPath can be pointed to the img_auth.php script ( $wgUploadPath = $wgScriptPath."/img_auth.php"; ) - see  for instructions.