public function getPostalCodes($elementIdx = 0)
    {
        if (true === array_key_exists($elementIdx, $this->postalCodes)) {
            return $this->postalCodes[$elementIdx];
        }

        if (false === array_key_exists($elementIdx, $this->response['elements'])) {
            throw new \Exception('Oups...');
        }

        if (true === array_key_exists('addr:postcode', $this->response['elements'][$elementIdx]['tags'])) {
            $postcode = $this->response['elements'][$elementIdx]['tags']['addr:postcode'];
            $this->postalCodes[$elementIdx] = explode(';', $postcode);

            // Ok... let's free a little bit of memory
            unset($this->response['elements'][$elementIdx]['tags']['addr:postcode']);
        } else {
            $this->postalCodes[$elementIdx] = null;
        }

        return $this->postalCodes[$elementIdx];
    }