public static function get_slide_by_id($dataDir = null)
 {
     # Instantiate Presentation class that represents the presentation file
     $pres = new Presentation($dataDir . 'Aspose.pptx');
     # Getting Slide ID
     $id = $pres->getSlides()->get_Item(0)->getSlideId();
     # Accessing Slide by ID
     $slide = $pres->getSlideById($id);
     print "Slide: " . $slide . PHP_EOL;
 }