This is a PHP script that will proxy GET requests (like from pfSense for example) to update a given DNS record.
The script is called like this:
https://ip_or_domain/miabproxy.php?address=ddns-address.example.com
curl -X PUT --user username@example.com:password https://ip_or_domain/miabproxy.php?address=ddns-address.example.com