Update do.de FlexDNS from OpenWRT, with IPv4 and IPv6 prefix support (make sure /tmp is a tmpfs to not kill your flash!)

update-ddns.php

#!/usr/bin/env php-cli
<?php
$url = 'https://ddns.resellerinterface.de/';
$username = 'DDNS-';
$password = '';

$saved = json_decode(file_get_contents("/tmp/ddns.json"), true);

$ipv6json = `ip -6 --json addr show dev br-lan`;
$ipv6 = parse_json($ipv6json);

$ipv4json = `ip -4 --json addr show dev pppoe-wan`;
$ipv4 = parse_json($ipv4json);

$updateSuccess = true;

if ($ipv4 != $saved["ipv4"])
{
	error_log("Updating ipv4 to " . $ipv4);

	$return = file_get_contents($url . '?' . http_build_query([
		"username" => $username,
		"password" => $password,
		"myip" => $ipv4
	]));

	error_log($return);

	if (strpos($return, "good") === false && strpos($return, "nochg") === false)
	{
		$updateSuccess == false;
	}
}

if ($ipv6 != $saved["ipv6"])
{
	error_log("Updating ipv6 to " . $ipv6);

	$return = file_get_contents($url . '?' . http_build_query([
		"username" => $username,
		"password" => $password,
		"ip6lanprefix" => str_replace("::1", "::/64", $ipv6)
	]));

	error_log($return);

	if (strpos($return, "good") === false && strpos($return, "nochg") === false)
	{
		$updateSuccess == false;
	}
}


if ($updateSuccess)
{
	file_put_contents("/tmp/ddns.json", json_encode([
		"ipv6" => $ipv6,
		"ipv4" => $ipv4
	], JSON_PRETTY_PRINT));
}

function parse_json(string $json)
{
	$data = json_decode($json, true);
	foreach ($data[0]["addr_info"] as $ipaddress)
	{
		if ($ipaddress["scope"] == "global")
		{
			return $ipaddress["local"];
		}
	}

	return false;
}