如何使一个子文件夹在谷歌驱动器执行后，这个脚本文件夹使在根

如何在google drive中创建子文件夹执行此脚本后，文件夹make在根目录

enter code here
$parentId=$par_idpath;
$file = new Google_DriveFile();
$file->setTitle($dir_name);  
$mimeType= gdrive_files::$mime_types['folder'];
$file->setMimeType($mimeType);
// Set the parent folder.
if ($parentId ) 
{
$parent = new Google_ParentReference();
$parent->setId($parentId);
$file->setParents(array($parent));
}
try {
$createdFile = $service->files->insert($file, array(
  'mimeType' => $mimeType,
));
} catch (Exception $e) {
  $this->err=$e->getMessage();