<?php
        
require "class-IXR.php";  

$USER = 'admin';
$PASS = 'AB';

$client = new IXR_Client('http://wordpress.com/xmlrpc.php');
                
if (!$client->query('wp.getCategories','', $USER, $PASS)) 
{  
    echo $client->getErrorCode() . ":" . $client->getErrorMessage();
}