Here's my thoughts for updating my ISPConfig3 MyDNS when my dynamic IP changes. I haven't had it change yet so I'm not 100% sure it's going to work.
On a remote server that has server side includes there is ip.shtml that contains only this line
<!--#echo var="REMOTE_ADDR" -->
When accessed this will give the current actual IP to my local server. The remote server is outside my local router.
Then there is a cron job running update_ip_address.php every 10 minutes. This file outputs to dynamic.html which is just an indication if something changed or not.
$db_server = 'localhost';
$db_user = 'root';
$db_password = 'password';
$echo_page = 'http://remote.example.com/ip.shtml';
$echoed_ip = trim(file_get_contents($echo_page));
$con = mysql_connect($db_server,$db_user,$db_password);
if (!$con) die('Could not connect: ' . mysql_error());
$table_data = mysql_query("SELECT * FROM dns_rr");
$change_flag = false;
while ($item_data = mysql_fetch_array($table_data))
if ($item_data['type'] == 'A')
$stored_ip = trim($item_data['data']);
if (!($stored_ip == $echoed_ip)) $change_flag = true;
echo date('l jS F Y h:i:s A');
echo ' ... IP Changed from '.$stored_ip.' to '.$echoed_ip.'.';
mysql_query("UPDATE dns_rr SET data='$echoed_ip' WHERE type='A'");
echo ' ... No Change.';
Basically, it gets the current IP echoed from the remote host, compares it to all the A records in the database that ISPConfig3 MyDNS is using, then UPDATEs them if they are different.
I haven't had my IP address change yet but this seems like it should work. Thoughts? Comments?