What does "Unable to move '/'" mean in PHP's move_uploaded_file() function?

edit

The error message "Unable to move '/'" in PHP's moveuploadedfile() function indicates that the file upload failed because the destination directory specified for moving the uploaded file is invalid or inaccessible. The '/' character is the root directory of the file system and may be used as a prefix to indicate an absolute path. This error message may occur if the destination directory does not exist, or if the permissions on the directory prevent moving the file to that location.