How to add framework codeigniter 3 HMVC?

[CanD62]

i use codeigniter 3 HMVC, and show error in browser =>> This site can’t be reached

my code in controller

defined('BASEPATH') OR exit('No direct script access allowed');
    use PDFMerger\PDFMerger;
    require_once APPPATH . "libraries/PDFMerger.php";
class Cetak_PDF extends MY_Controller {

public function combie_pdf()
    {
$pdf = new PDFMerger();

$pdf->addPDF('D:/htdocs/myproject/assets/doc1.pdf', 'all');
$pdf->addPDF('D:/htdocs/myproject/assets/doc2.pdf', 'all');
$pdf->merge('browser', 'TEST2.pdf');
}

}