private function hash(int $length):string {
		$char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; // strlen($char) = 62
		$hash = '';
		for( $i=0; $i < $length; $i++ )
			$hash .= $char[random_int(0,61)];
		return $hash;
	}