Searching in the web and in Stack Overflow I didn’t find post where the problem was solved

I’ve this code

        $params = array();
        $file = new Google_Service_Drive_DriveFile();
        $file->setProperties("myProp"=>null);
        $response = $driveService->files->update($fileid,$file,$params);

and has no effect… the property mantains its original value (set with the same method)