protected function build()
    {
        $this->rawXml = $this->buildXML();

        $this->client->setDefaultOption('headers', array(
            'Content-Type' => 'application/x-www-form-urlencoded'
        ));

        $this->request = $this->client->post(null, null, array(
            "xml" => ($this->rawXml->saveXML())
        ));
    }