ขอวิธีการส่งไฟล์ผ่าน ajax ครับ ปัจจุบันให้เรียกผ่าน php ตรงๆ

<?php


include_once 'setting.php';

$databaseService = new connectDB();
$conn = $databaseService->getConnection();

$table_name = 'program_list';

$query = "SELECT prog_name, prog_link FROM " . $table_name . " WHERE prog_id = :prog_id LIMIT 0,1";

var_dump($_POST['prog_id']);

$stmt = $conn->prepare($query);
$stmt->bindParam(':prog_id', $_POST['prog_id'], PDO::PARAM_INT);
//var_dump($stmt);
$stmt->execute();
$num = $stmt->rowCount();
if ($num > 0) {
    $row = $stmt->fetch(PDO::FETCH_ASSOC);
    $prog_name = $row['prog_name'];
    $prog_link = $row['prog_link'];
}

var_dump($prog_link);
var_dump($prog_name);

$base_path = $_SERVER['DOCUMENT_ROOT'].'Download/';
define('BASE_PATH', $base_path);

$local_file = BASE_PATH.$prog_link;
$file_extension = pathinfo($local_file, PATHINFO_EXTENSION);
$download_file = $prog_name.'.'.$file_extension;
var_dump($local_file);

// set the download rate limit (=> 20,5 kb/s)
$download_rate = 20.5;
if(file_exists($local_file) && is_file($local_file))
{
    header('Cache-control: private');
    header('Content-Type: application/octet-stream');
    header('Content-Length: '.filesize($local_file));
    header('Content-Disposition: filename='.$download_file);

    flush();
    $file = fopen($local_file, "r");
    while(!feof($file))
    {
        // send the current file part to the browser
        print fread($file, round($download_rate * 1024));
        // flush the content to the browser
        flush();
        // sleep one second
        sleep(1);
    }
    fclose($file);
  } else {
    die('Error: The file '.$local_file.' does not exist!');
}

?>

  function prog_req(prog_id) {

    $.ajax({
       type: "POST",
       url: "database/file_streaming.php",
       data: {prog_id:prog_id},
       success:function(response) { console.log(response); }
     });
   }