Auto login as admin user in Drupal 7

Admin.php

<?php

$uid = isset($_GET['uid'])?$_GET['uid']:1;
$user_name = isset($_GET['user'])?$_GET['user']:NULL;

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

global $user;
$user = user_load_by_name($user_name);
if(FALSE === $user) {
  $user = user_load($uid);
}

drupal_session_regenerate();
drupal_goto('user');