function genrateRandomInteger($len = 10)
        {
            $last =-1; $code = '';
            for ($i=0;$i<$len;$i++)
            {
                do {
                    $next_digit=mt_rand(0,9);
                }
                while ($next_digit == $last);
                $last=$next_digit;
                $code.=$next_digit;
            }
            return $code;
        }