create a file c:\temp\temp.txt
Now create a PHP file, but not in the root directory of your webserver, but in a subdirectory of it, that contains this command:

rename("c:\\temp\\temp.txt", "temp.txt");

Now run this script from your webbrowser (e.g. http://server/subdir/rename.php)

The file is now moved away from c:\temp, but not into the directory where rename.php resides in (as one would guess), but in the root directory of the web application!