<?php
# PHP script for very simple dynamic DNS updates 
#
# this script was published in http://pablohoffman.com/articles and 
# released to the public domain by Pablo Hoffman on 27 Aug 2006

# CONFIGURATION BEGINS -------------------------------------------------------
# define host and passwords here 
$hosts = array(
    'client' => 'secret',
    'host2'  => 'secret2',
);
$zone = "dyn.domain.com"; # the dynamic DNS zone
$dnsserver = "localhost"; # authorative DNS server for the zone above
# CONFIGURATION ENDS ---------------------------------------------------------


$ip = $_SERVER['REMOTE_ADDR'];
$host = $_GET['host'];
$pass = $_GET['pass'];
$tmpfile = trim(`mktemp /tmp/nsupdate.XXXXXX`);

if ((!$host) or (!$pass) or (!($hosts[$host] == $pass))) { 
    echo "FAILED";
    exit; 
}

$oldip = trim(`host $host.$zone | cut -d ' ' -f 4`);
if ($ip == $oldip) {
    echo "UNCHANGED";
    exit;
}

echo "$ip - $oldip";

$nsucmd = "server $dnsserver
zone $zone
update delete $host.$zone A
update add $host.$zone 3600 A $ip
send
";

$fp = fopen($tmpfile, 'w');
fwrite($fp, $nsucmd);
fclose($fp);
`/usr/bin/nsupdate $tmpfile`;
unlink($tmpfile);
echo "OK";
?>