Get a Hashed SubDirectory

/**
 * get a hashed subdir.
 *
 * @author liuran
 */
function getHashedDir ()
{	
	$key_1 = rand (32768, 65535);
	$key_2 = microtime ();
	$key_3 = sha1 (time ());
 
	$sid = md5 ($key_1 . $key_3 . $key_2);	
	$hash_dir = substr ($sid, 0, 2) . '/' . substr ($sid, 15, 2) . '/';
	return $hash_dir;
}