## netmask to CIDR
function inet_ntocidr($netmask)
{
  $netmask = trim($netmask);

  $bits = decbin(abs(sprintf('%u',ip2long($netmask))));
  $cidr = strpos($bits,'0') + 0;

  return ($cidr > 0) ? $cidr : 32;
}

한글사랑