PHP integration with TNT (that doesn't work)

gistfile1.php

$this->template = 'sale/xml/tnt_r.tpl';
$xml_ = $this->render();  // build the xml with the order data

try {
    $gsearch = new SoapClient('https://www.mytnt.it/ResiService/ResiServiceImpl.wsdl');
    $result = $gsearch->__soapCall('getPDFLabel', array(array('inputXml'=>$xml_)));
    $result2 = $result->getPDFLabelReturn;
    
    if ($result2->documentCorrect == 1 && strlen($result2->binaryDocument)>0){
        // sparare il pdf $result2->binaryDocument;
        header('Content-Description: File Transfer');
        header('Content-Type: application/pdf');
        header('Content-Disposition: attachment; filename="label.pdf"');
        header('Expires: 0');
        echo $result2->binaryDocument;
    } else {
        // sparare l'xml $result2->outputString;
        header('Content-Type: text/txt');
        header('Expires: 0');
        echo $result2->outputString;
    }
    unset($gsearch);
} catch (SoapFault $e) {
    header('Content-Type: text/html');
    header('Expires: 0');
    print_r($e);
}