private function getSession()
    {
        $vars = array(
            'method' => 'auth.getSession',
            'api_key' => $this->apiKey,
            'token' => $this->token
        );
        $sig = $this->apiSig($this->apiSecret, $vars);
        $vars['api_sig'] = $sig;

        if ($call = $this->apiGetCall($vars)) {
            $this->username = (string) $call->session->name;
            $this->sessionKey = (string) $call->session->key;
            $this->subscriber = (string) $call->session->subscriber;
        } else {
            return false;
        }
    }