public static function random($len = 20, $char = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789') {
		$str = '';
		for ($ii = 0; $ii < $len; $ii++) {
			$str .= $char[mt_rand(0, strlen($char) - 1)];
		}

		return $str;
	}