Swiss post tracking web service implementation using php soap

Question

I'm working on a E-commerce site on which orders are placed. i want to track that delivery status of order and I need to give a status of order to user over mail.

I have to use Swiss Post Tracking Web Service API. Can anyone show me how to do so? I am new to SOAP WSDL.

From my understanding i did this now how to go further? My code below its just basic client i need to:

I need to track the delivery status

Below is my code

    $wsdl   = "https://webservices.post.ch:17005/IN_MYPBxTT/services/TrackAndTraceDFU.ws?WSDL
    $username = 'username';
    $password = 'password';
    $trace = True;

    $soapConfig = array(
        'login'=>$username,
        'password'=>$password,
        'trace'=>$trace,
        'keep_alive'=>TRUE,
        'encoding'=>'utf8',
        'connection_timeout'=>90,
    );
   $soapClient = new SoapClient($wsdl, $soapConfig);

   try {
        $xml = '<soapenv:Envelope xmlns:soapenv=“http://schemas.xmlsoap.org/soap/envelope/“
                xmlns:req=“http://www.post.ch/npp/trackandtracews/v02/shipmentssearch/req“>
                    <soapenv:Header/>
                    <soapenv:Body>
                        <req:ShipmentsSearch>
                            <language>de</language>
                            <ShipmentNumbers>
                                <ShipmentNumber>99.60.122566.27198756</ShipmentNumber>
                            </ShipmentNumbers>
                            <Identity>?</Identity>
                            <Version>2.4</Version>
                        </req:ShipmentsSearch>
                    </soapenv:Body>
                </soapenv:Envelope>';
    
        $args = array(new SoapVar($xml, XSD_ANYXML));  
        $res  = $this->_soapClient->__soapCall('ShipmentsSearch', $args);
        return $res;
    } catch (SoapFault $e) {
        echo "Error: {$e}";
    }
    
    echo "<hr>Last Response";
    echo "<pre>", htmlspecialchars($this->_soapClient->__getLastResponse()), "</pre>";
    die;

I am using this code but getting below error

    Error: SoapFault exception: [env:Client] Internal Error in /directory-name/ConsignmentWebService.php:114 
Stack trace: #0 /directory-name/ConsignmentWebService.php(114): SoapClient->__soapCall('ShipmentsSearch', Array)

and get the response like this

Last Request
<?xml version='1.0' ?>
<env:Envelope xmlns:env='http://schemas.xmlsoap.org/soap/envelope/'>
<env:Body>
<env:Fault>
<faultcode>env:Client</faultcode>
<faultstring>Internal Error</faultstring>
</env:Fault>
</env:Body>
</env:Envelope>

I referred this tutorial https://www.post.ch/en/business-solutions/digital-commerce/notification-services/sendungsinformationen

please help me I am new in soap
Updated Code who are looking for solution

        $wsdl   = "https://webservices.post.ch:17005/IN_MYPBxTT/services/TrackAndTraceDFU.ws?WSDL
        $username = 'username';
        $password = 'password';
        $trace = True;
    
        $soapConfig = array(
            'login'=>$username,
            'password'=>$password,
            'trace'=>$trace,
            'keep_alive'=>TRUE,
            'encoding'=>'utf8',
            'connection_timeout'=>90,
        );
       $soapClient = new SoapClient($wsdl, $soapConfig);

       $response = null;
        $generateRequest = array(
            'language'=>'de',
            'ShipmentNumbers'=>array(
                'ShipmentNumber'=>$tracking_code,  //your track code
            ),
            'Identity'=>'?',
            'Version'=>2.4
        );
        try {
            $response = $this->_soapClient->ShipmentsSearch($generateRequest);
            return $response;
        } catch (SoapFault $fault) {
            echo('Error in Getting Delivery Status: '. $fault->__toString() .'<br />');
            echo '<pre>';
            var_dump($this->_soapClient->__getLastResponse());
            echo '</pre>';
            die();
        }