public static function getRandomString(int $length = 64) : string
    {
        $characters = "01234567890123456789";
        $characters .= "abcdefghijklmnopqrstuvwxyz";

        $string_generated = "";

        while ($length--) {
            $string_generated .= $characters[mt_rand(0, 45)];
        }

        return $string_generated;
    }