How to Download File using PHP

?php
if(isset($_GET['download_file_name'])){
      $mypath = $_SERVER['DOCUMENT_ROOT']."/download/"; // change the path to fit your websites document structure
      $file_location = $mypath.$_GET['download_file_name'];
      if ($fd = fopen ($file_location, "r")) {
            $fsize = filesize($file_location);
            $path_parts = pathinfo($file_location);
            $ext = strtolower($path_parts["extension"]);
            switch ($ext) {
                  case "pdf":
                  header("Content-type: application/pdf"); // add here more headers for diff. extensions
                  header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\""); // use 'attachment' to force a download
                  break;
                  default;
                  header("Content-type: application/octet-stream");
                  header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
            }
            header("Content-length: $fsize");
            header("Cache-control: private"); //use this to open files directly
            while(!feof($fd)) {
                  $buffer = fread($fd, 2048);
                  echo $buffer;
            }
      }
      fclose ($fd);
      exit;
}
?>
<a href="download.php?download_file_name=dum.pdf">Download here</a>