Как исправить ошибку «Error: Class 'SQLite3' not found in /var/www/test.site/public_html/news/NewsDB.class.php on line 17»?

class NewsDB implements INewsDB{
    const DB_NAME = __DIR__.'/news.db';
    private $_db;

    function __get($name) {
      // TODO: Implement __get() method.
      if($name == 'db'){
        return $this->_db;
      }
      throw new Exception('Unknown property!!!');
    }

    function __construct() {
      $this->_db = new SQLite3(self::DB_NAME);
    }

    function __destruct() {
      // TODO: Implement __destruct() method.
      unset($this->_db);
    }

    function saveNews($title, $category, $description, $source) {
      // TODO: Implement saveNews() method.
    }

    function getNews() {
      // TODO: Implement getNews() method.
    }

    function deleteNews($id) {
      // TODO: Implement deleteNews() method.
    }
  }

Fatal error: Uncaught Error: Class 'SQLite3' not found in /var/www/test.site/public_html/news/NewsDB.class.php on line 17