Wordpress - How to extend xmlrpc to retrieve archives

gistfile1.php

<?php
/**
 * Plugin Name: XMLRPC archive
 * Plugin Uri: http://localhost/
 * Description: Extend Wordpress API to get archives
 * Version 1.0
 * Author: John Doe
 */
 
 
 // tested on wordpress 3.5.2
 if (!function_exists('add_filter')) {
   die('Do not call me directly.');
 }
 
 function xmlrpc_archive_get_archives() 
 {
   $links = array();
   $archives = wp_get_archives(array('echo' => 0, 'format' => 'custom'));
   foreach (simplexml_load_string('<root>' . $archives . '</root>')->children() as $a) {
     $links[] = array('href' => (string) $a['href'], 'title' => (string) $a['title']);
   }
   
   return $links;
 }
 
 function __xmlrpc_archive_methods($methods) 
 {
   if (!isset($methods['wp.getArchives'])) { // XMLRPC method name
     return $methods['wp.getArchives'] = 'xmlrpc_archive_get_archives'; // callback
   }
 }
 
 add_filter('xmlrpc_methods', '__xmlrpc_archive_methods');