PHP: Curl-Request with XML-Response

I send a GET request with PHP curl and get an XML file as response.

$curl_session = curl_init();
curl_setopt($curl_session, CURLOPT_URL, $url);
curl_setopt($curl_session, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($curl_session, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/xml',
    'Accept-Encoding: gzip, deflate, br'
));
$result = curl_exec($curl_session );
curl_close($curl_session);

Unfortunately PHP returns me a string.

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If I save the response directly in an XML file, then it works. However, I would like to work with the XML data without having to save it first. simplexml_load_string does not work, because the XML tag is missing in the string. How can I work directly with the XML data?