Empty associative array in soap server

[gotha]

Hi, I am testing the example in the documentation: http://besim.pl/SoapBundle/soapserver/tutorial/associative_array.html

my code is like this:

/**
     * @Soap\Method("sendAssocArray")
     * @Soap\Param("assocArray", phpType = "BeSimple\SoapCommon\Type\KeyValue\String[]")
     * @Soap\Result(phpType = "BeSimple\SoapCommon\Type\KeyValue\String[]")
     */
    public function sendAssocArrayOfStringAction(array $assocArray)
    {
        return $assocArray;
    }

My client call it like this:

$client = new SoapClient("http://localhost:9999/app_dev.php/ws/MyService?wsdl", array('cache_wsdl' => WSDL_CACHE_NONE));
$response = $client->sendAssocArray(["name" => "Ivan", "lastName" => "Petrov"]);
var_dump($response);

$response is empty stdClass and when I check $assocArray is empty too.

Is this some kind of bug or I am doing something wrong ?