/**
 * Function to check the passed address is within the passed subnet
 *
 * The parameter is a comma separated string of subnet definitions.
 * Subnet strings can be in one of three formats:
 *   1: xxx.xxx.xxx.xxx/xx
 *   2: xxx.xxx
 *   3: xxx.xxx.xxx.xxx-xxx   //a range of IP addresses < 256
 * Code for type 1 modified from user posted comments by mediator at
 * {@link http://au.php.net/manual/en/function.ip2long.php}
 *
 * @param string $addr    The address you are checking
 * @param string $subnetstr    The string of subnet addresses
 * @return boolean
 */
function address_in_subnet($addr, $subnetstr) {

    $subnets = explode(',', $subnetstr);
    $found = false;
    $addr = trim($addr);

    foreach ($subnets as $subnet) {
        $subnet = trim($subnet);
        if (strpos($subnet, '/') !== false) { /// type 1
            list($ip, $mask) = explode('/', $subnet);
            $mask = 0xffffffff << (32 - $mask);
            $found = ((ip2long($addr) & $mask) == (ip2long($ip) & $mask));
        } else if (strpos($subnet, '-') !== false)  {/// type 3
            if (substr($subnet,15,1) == '-') {  //filters out malformed addresses
                $addrsubstr = substr($addr,12,3);
                $commonstring = substr($subnet,0,11);
                $startno = substr($subnet,12,3);
                $endno = substr($subnet,16,3);
                if(substr($addr,0,11) ==  $commonstring){
                    if(($startno <= $addrsubstr) && ($endno >= $addrsubstr)){
                        $found = true;
                    }
                }
            }
        } else { /// type 2
            $found = (strpos($addr, $subnet) === 0);
        }

        if ($found) {
            break;
        }
    }
    return $found;
}