You can use this to alter your DNS entries at GratisDNS. cURL required.
See example.php for how to use this and use dyndns.php to automatically update a record with a dynamic ip.
Feel free to fork and if you can improve this script please make a pull request. :)
This php script use 'PHP Simple HTML DOM Parser' to parse the HTML. http://simplehtmldom.sourceforge.net I would love to require this thru Packagist, but it is not included.