function random_string($length) {
    $string = "";


    for ($i = 0; $i <= ($length/32); $i++)
        $string .= md5(time()+rand(0,99));

    $max_start_index = (32*$i)-$length;
  $random_string = substr($string, rand(0, $max_start_index), $length);

    return $random_string;
}