Basic PHP File download

basic_php_file_download.php

<?php   
$file = '/tmp/file.xml';

if (file_exists($file)) {
      header('Content-Description: File Transfer');
      header('Content-Type: application/octet-stream');
      header('Content-Disposition: attachment; filename='.basename($file));
      header('Content-Transfer-Encoding: binary');
      header('Expires: 0');
      header('Cache-Control: must-revalidate');
      header('Pragma: public');
      header('Content-Length: ' . filesize($file));
      ob_clean();
      flush();
      readfile($file);
      exit;
}
?>