无法传输已发送的pdf：标头

Question

How to clear this problems for dompdf file so please help me.

require_once 'dompdf/autoload.inc.php';

//Reference the Dompdf namespace
use Dompdf\Dompdf;
$html  = $this->load->view('mobileuserprint',$customers,true);
$domdpf = new Dompdf();
$domdpf->loadHtml($html);
$domdpf->setPaper('A4','landscape');
$domdpf->render();