验证后使用ajax下载pdf

Question

$(".getmydeal").click(function(){
    var dealid = $(this).data("deal");
    if(dealid != ""){
    $.ajax({
        type : "POST",
        url : "ajax-download-deal.php",
        data : {dealid:dealid},
        success : function(response) {
         //Some action to perform
        }
    });
   }
});

单击getmydeal时调用简单的ajax。现在问题是我需要在验证用户是否登录和订阅后下载pdf。所以我使用php如下

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_SESSION['portaluser'])) {

    $mymobile = mysqli_real_escape_string($conn,$_POST['dealid']);

    //This is my code for downloading pdf

    $file = "http://www.pdf995.com/samples/pdf.pdf";
    header('Content-Type: application/pdf');
    header("Content-Disposition: attachment; filename=\"$file\"");
    readfile($file);

}else{

    //User Must Login First

}

但是服务器没有下载该文件。所以可以使用ajax在php文件上下载pdf。