Check if an IP is from private subnet

<?php

function inet_private($addrString)
{
  $addr = inet_pton($addrString);
  if(strlen($addr) !== 4)
    throw new Exception('Only valid IPv4 addresses are currently supported.');

  $ta = unpack('n*', $addr);
  $addr = reset($ta);
  return $addr === 49320 // 192.168.0.0/16
    || ($addr &~ 15) === 44048 // 172.16.0.0/12
    || ($addr &~ 255) === 32512 // 127.0.0.0/8
    || ($addr &~ 255) === 2560; // 10.0.0.0/8
}