Drupal 7 varnish status file

<?php
// Register our shutdown function so that no other shutdown functions run before this one.
// This shutdown function calls exit(), immediately short-circuiting any other shutdown functions,
// such as those registered by the devel.module for statistics.
define('DRUPAL_ROOT', getcwd());
register_shutdown_function('status_shutdown');
function status_shutdown() {
  exit();
}

// Drupal bootstrap.
require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);

// Build up our list of errors.
$errors = array();

// Check that the main database is active.
$account = db_select('users','u')
        ->fields('u')
        ->condition('uid',1,'=')
        ->execute()
        ->fetchObject();

if ($account->uid != 1) {
  $errors[] = 'Master database not responding.';
}

// Check that the website is online
$mode_obj = db_select('variable', 'v')->fields('v')->condition('name', "maintenance_mode", "=")->execute()->fetchObject();
if($mode_obj->value)
{
  $mode = unserialize($mode_obj->value);
  if ($mode != 0) {
    $errors[] = 'Site offline';
  }
}
else
{
  $errors[] = 'Could not fetch the offline status of the website.';
}

// Check that the files directory is operating properly. Do not use variable_get, not initialized yet.
$files_path_obj = db_select('variable', 'v')->fields('v')->condition('name', "file_public_path", "=")->execute()->fetchObject();
if($files_path_obj->value)
  $files_path = unserialize($files_path_obj->value);
if ($files_path && $test = tempnam($files_path, 'status_check_')) {
  if (!unlink($test)) {
    $errors[] = 'Could not delete newly created file in the files directory.';
  }
}
else {
  $errors[] = 'Could not create a file in the files directory.';
}

// Print all errors.
if (count($errors) > 0) {
  header('HTTP/1.1 500 Internal Server Error');
  print 'NOK' . ' 500' . '<br />';
  print implode("<br />\n", $errors);
}
else {
  // Split up this message, to prevent the remote chance of monitoring software
  // reading the source code if mod_php fails and then matching the string.
  print 'OK' . ' 200';
}

// Exit immediately, note the shutdown function registered at the top of the file.
exit();