DownloadFile.php

<?php

$path = "UploadedFile/"; // change the path to fit your websites document structure

$dl_file = preg_replace("([^\w\s\d\-_~,;:\[\]\(\).]|[\.]{2,})", '', $_GET['down']); // simple file name validation
$dl_file = filter_var($dl_file, FILTER_SANITIZE_URL); // Remove (more) invalid characters
$fullPath = $path.$dl_file;

if(file_exists($path.$dl_file)){
  if ($fd = fopen ($fullPath, "r")) {
      $fsize = filesize($fullPath);
      $path_parts = pathinfo($fullPath);
      $ext = strtolower($path_parts["extension"]);
      switch ($ext) {
          case "pdf":
          header("Content-type: application/pdf");
          header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\""); // use 'attachment' to force a file download
          break;
          // add more headers for other content types here
          default;
          header("Content-type: application/octet-stream");
          header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
          break;
        }
        header("Content-length: $fsize");
        header("Cache-control: private"); //use this to open files directly
        while(!feof($fd)) {
          $buffer = fread($fd, 2048);
          echo $buffer;
        }
      }
}
else{
  ?>
  <script>
    alert('Sorry. This file does not exists!.');
    window.location.href='facWLAP.php';
  </script>
  <?php
}
fclose ($fd);
exit;