private function createSalt($max = 15)
    {
        $characterList = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        $i = 0;
        $salt = "";
        do {
            $salt .= $characterList{mt_rand(0,strlen($characterList)-1)};
            $i++;
        } while ($i < $max);

        return $salt;
    }