How to display a webservice response with nuSOAP php?

I’m using an old version of PHP, 5.3.9. To get around TLS problems, I’m using nuSOAP to connect to a webservice.

The connection is ok but the response returned by the webservice is empty and I get no error.

With a more recent version of PHP I do this:

    $client = new SoapClient($wsdlUrl, $options);
   //Here we call REQUEST URL
    $output = $client->__doRequest($xmlrequest, $requestUrl, $action, 1);

    // Affichez la réponse SOAP
    echo "Réponse SOAP :<br>";
    echo htmlentities($output);

And I get the displayed response.

With nuSOAP I do this but the response is empty:

$response = $client->send($xmlrequest, $action, '', $requestUrl);

echo "Réponse de la méthode SOAP : ";
echo htmlentities($response);

How can I get the same result?

My entire code:

<?php

// Include the NuSOAP file
require_once('nusoap-0.9.5/lib/nusoap.php');

// Define the URL of the Web service
$wsdlUrl = 'https://ws.chronopost.fr/shipping-cxf/ShippingServiceWS?wsdl';
$requestUrl = 'https://ws.chronopost.fr/shipping-cxf/ShippingServiceWS';

// Create a NuSOAP client
$client = new nusoap_client($wsdlUrl, true);

// Check if there was an error during client creation
$err = $client->getError();
if ($err) {
    // If there was an error during client creation, display the error message
    echo "Error creating client: " . $err;
    exit();
} else {
    // If no error was detected, display "connection successful"
    echo "Connection successful";
}

// Define the SOAP action and the content of the request
$action = 'euExpressRateBook_providerServices_ShipmentHandlingServices_Binder_createShipmentRequest';
$xmlrequest = '<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:cxf="http://cxf.shipping.soap.chronopost.fr/">
<soapenv:Header/>
<soapenv:Body>
//rest of the code
</soapenv:Body>
</soapenv:Envelope>';

// Send the SOAP request
$response = $client->send($xmlrequest, $action, '', $requestUrl);

// Display the SOAP request response
echo "SOAP method response: ";
echo htmlentities($response);

Thanks for your help,