countrySubdivision level is missing in your output object.
Try this :
Code:
$url="http://ws.geonames.org/countrySubdivision?lat=47.03&lng=10.2&style=full";
$output = file_get_contents($url);
$xml = simplexml_load_string($output);
echo "<pre>";print_r($xml);echo "</pre>";
echo $xml->countrySubdivision->countryName."<br />";
echo $xml->countrySubdivision->adminName1."<br />";