# nginx config
server {
    listen 80;
    server_name home.cars10k.de;

    root /var/www/home/;
    index index.php;

#    location / {
#        rewrite ^ /dyndns.php;
#    }

    location ~ \.php {
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
        fastcgi_pass unix:/var/run/php/php7.0-fpm-home.sock;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;
        fastcgi_param front_controller_active true;
        fastcgi_intercept_errors on;
        fastcgi_request_buffering off;

    }
}




# script dyndns.php
<h1>If you are seeing this than something went wrong.</h1>
<?php
// Set a secure password
$password = 'NmU3ZjMyMTU2ZWQ4N2I0';
// Variables
$ip_file = "saved_ip.txt";
$sent_password = $_GET["password"];
$ip = $_GET["ip"];
$secure = $_GET["s"];
$port = $_GET["p"];

if (file_exists($ip_file)) {
    // if a password and an ip address where sent we assume it's an update from the router, so save that
    if (isset($sent_password) && isset($ip)) {
        if ($sent_password == $password) {
            $file_handle = fopen("$ip_file", "w");
            fwrite($file_handle, $ip);
            fclose($file_handle);
            header( "HTTP/1.1 200 OK" );
        } else {
            header("HTTP/1.1 401 Unauthorized");
            exit;
        }
    } else {
        // normal request: we want to redirect
        $file_handle = fopen("$ip_file", "r+");
        $saved_ip = trim(fread($file_handle, filesize($ip_file)));
        fclose($file_handle);

        if (isset($port)) {
            $url = $saved_ip . ":" . $port;
        } else {
            $url = $saved_ip;
        }

        if (isset($secure)) {
            $url_with_protocol = "https://" . $url;
        } else {
            $url_with_protocol = "http://" . $url;
        }
        header("Location: $url_with_protocol");
    }
}