public function containers($enabledOnly = NULL) {
    $client = \HPCloud\Transport::instance();
    $url = $this->url . '/?format=json';

    if ($enabledOnly) {
      $url .= '&enabled_only=true';
    }
    // DEVEX-1733 suggests that this should result in the
    // server listing only DISABLED containers.
    elseif ($enabledOnly === FALSE) {
      $url .= '&enabled_only=false';
    }

    $headers = array(
      'X-Auth-Token' => $this->token,
    );

    $response = $client->doRequest($url, 'GET', $headers);

    $raw = $response->content();
    $json = json_decode($raw, TRUE);

    return $json;
  }