code: function MsPowerpoint_SlideIsIt($FileName) {
  		$this->MsPowerpoint_InitSlideLst();
  		foreach ($this->OpenXmlSlideLst as $i => $s) {
  			if ($FileName==$s['file']) return true;
  		}
  		return false;
  	}
docs: Return true if the file name is a slide.