php cidr前缀为netmask

function CIDRtoMask($int) {
    return long2ip(-1 << (32 - (int)$int));
}

  function cidr2NetmaskAddr ($cidr) {

    $ta = substr ($cidr, strpos ($cidr, \'/\') + 1) * 1;
    $netmask = str_split (str_pad (str_pad (\'\', $ta, \'1\'), 32, \'0\'), 8);

    foreach ($netmask as &$element)
      $element = bindec ($element);

    return join (\'.\', $netmask);

  }

  echo cidr2NetmaskAddr (\'194.234.213.0/28\');

  function createNetmaskAddr ($bitcount) {

    $netmask = str_split (str_pad (str_pad (\'\', $bitcount, \'1\'), 32, \'0\'), 8);

    foreach ($netmask as &$element)
      $element = bindec ($element);

    return join (\'.\', $netmask);

  }

  echo createNetmaskAddr (28);