Soap server Symfony how to set response

I am trying to implement a very simple soap call in Symfony3. It works perfectly but it return nothing.

In my controller I just call it like this

public function indexAction()
{
    $server = new \SoapServer($this->get('kernel')->getRootDir()."/../web/soap/test.wsdl");
    $server->setObject($this->get('serv.soapservice'));

    $response = new Response();
    $response->headers->set('Content-Type', 'text/xml; charset=ISO-8859-1');

    ob_start();
    $server->handle();
    $response->setContent(ob_get_clean());

    return $response;
}

And the called function looks like this

public function hello($param)
{
    return 'Hello, '.$param->name;
}

I tried it with SoapUI and it works perfectly, but the soap return is like this

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://localhost/symfony/test/web/app_dev.php/en/soap">
    <SOAP-ENV:Body>
       <ns1:helloResponse/>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

It doesn't return the response of the function like this

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://localhost/symfony/test/web/app_dev.php/en/soap">
    <SOAP-ENV:Body>
       <ns1:helloResponse>
           <out>Hello John</out>
       <ns1:helloResponse/>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

How can I return it?

I finally find the problem. I just have to change the way I return in my hello function. It looks like this now and works great.

public function hello($param)
{
    $response = array();
    $response['out']='Hello, '.$param->name;
    return $response;
}