Moved DynDNS Service from Apache to nginx

Hi,

i just moved my dyndns service from my apache2 server to my new nginx machine. While the service was working good on apache it didn´t on nginx.

The Fritzbox connects to my dyndns service via this link

http://dyn.myserver.co/myscript.php?pass=mypassword&meineip=<ipaddr>

Thats the script (myscript.php)

$pwort = 'mypassword';
$port = ':80';

$dyntxt = "my_IP.txt";
$pworttest = $_GET["pass"];
$IP = $_GET["meineip"];

if (file_exists($dyntxt)){if($pworttest==$pwort) { $a = fopen("$dyntxt", "w");
$dynamicip = $_SERVER["REMOTE_ADDR"];
fwrite($a, $IP);
fclose($a); } 
else { $a = fopen("$dyntxt", "r+"); 
$dynamicip = fread($a,filesize($dyntxt));
fclose($a);

$url="http://".$dynamicip."".$port; 
header("Location: $url");} }
?>

And here is my config for dyn.myserver.co on nginx:

server {
    listen 80;
    listen [::]:80;

    root /var/www/dyn;
    index index.php index.html index.htm;

    server_name dyn.myserver.co;

    location / {
        try_files $uri/ /index.php?$args;
    }
    error_page 404 /404.html;
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /var/www/dyn;
    }

    location ~ \.php$ {
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_index index.php;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }
}

The IP which is written in my_IP.txt is copied to the DNS Server by cronjob. That is working. For example: On my apache server i called the dyndns URL (http://dyn.myserver.co/myscript.php) and was redirected to the IP which was filled in my_IP.txt. On nginx it just shows me the content of myscript.php.

I think it´s a problem with the nginx config. Can anybody help me?