如何在word中使用Dompdf在ajax回调函数中

Question

I have searched a lot and tried in many ways I did not get a solution for this, in my code it showing filed whenever I click to download

my angular code is

$scope.downloadList = function () {
 Factory.downloadSubmissions($scope.Id, $scope.downloadType).then(function (response) {
                    var url = cf7_magick_object.ajax_url;
                    var link=document.createElement('a');

                    link.href=window.URL = url+"submission.pdf";

                    link.download= response.data;
                    link.click();
 });
    }; 

My ajax call back PHP function is

  public function downloadFormSubmissionCallback(){
    $formPostId     = (int)$_REQUEST['formId'];
    $downloadType   = $_REQUEST['downloadType'];
    $dompdf = new Dompdf();
         $dompdf->loadHtml('hello world');
         $dompdf->setPaper('A4', 'landscape');
         $dompdf->render();
         $output = $dompdf->output();

         echo json_encode($output);
    }

can anyone tell me where I am wrong?