via: http://www.hurricanesoftwares.com/wordpress-xmlrpc-posting-content-from-outside-wordpress-admin-panel/

wp-remote-post-2.php

<?php 
require_once("IXR_Library.php.inc");
 
$client->debug = true; //Set it to false in Production Environment
 
$title="Blog Title"; // $title variable will insert your blog title 
$body="Blog Content"; // $body will insert your blog content (article content)
 
$category="category1, category2"; // Comma seperated pre existing categories. Ensure that these categories exists in your blog.
$keywords="keyword1, keyword2, keyword3";
 
$customfields=array('key'=>'Author-bio', 'value'=>'Autor Bio Here'); // Insert your custom values like this in Key, Value format
 
 
    $title = htmlentities($title,ENT_NOQUOTES,$encoding);
    $keywords = htmlentities($keywords,ENT_NOQUOTES,$encoding);
 
    $content = array(
        'title'=>$title,
        'description'=>$body,
        'mt_allow_comments'=>0,  // 1 to allow comments
        'mt_allow_pings'=>0,  // 1 to allow trackbacks
        'post_type'=>'post',
        'mt_keywords'=>$keywords,
        'categories'=>array($category),
		'custom_fields' =>  array($customfields)
 
 
    );
 
// Create the client object
$client = new IXR_Client('Your Blog Path/xmlrpc.php');
 
 $username = "USERNAME"; 
 $password = "PASSWORD"; 
 $params = array(0,$username,$password,$content,true); // Last parameter is 'true' which means post immideately, to save as draft set it as 'false'
 
// Run a query for PHP
if (!$client->query('metaWeblog.newPost', $params)) {
    die('Something went wrong - '.$client->getErrorCode().' : '.$client->getErrorMessage());
}
else
    echo "Article Posted Successfully";
 
?>