public function saveExport($source, $filename) {
    $this->deleteExport($filename);

    if (!self::dirReady("{$this->path}/exports")) {
      throw new Exception("Unable to create directory for H5P export file.");
    }

    if (!copy($source, "{$this->path}/exports/{$filename}")) {
      throw new Exception("Unable to save H5P export file.");
    }
  }