public function getParams()
    {
        $params = array(
            'start' => $this->start, 'pageLength' => $this->pageLength,
            'view' => $this->view, 'format' => $this->format
        );
        if(!empty($this->options)) {
            $params['options'] = $this->options;
        }
        if(!empty($this->collection)) {
            $params['collection'] = $this->collection;
        }
        if(!empty($this->directory)) {
            $params['directory'] = $this->directory;
        }
        return $params;
    }