public function getWithOffers()
    {
        if ((int) $this->id <= 0) {
            throw new NullPointerException("Id is not set.");
        }
        
        // build url
        $url = $this->base_url . str_replace("{id}", $this->id, $this->_url_offers);
        // get data from server
        $data = $this->getDataFromUrl($url);
        // parse result set and get data as array
        $result = $this->parseJsonData($data);
        
        return $result;
    }