function serve($data = false)
    {
        if (!$data) {
            if (isset($_SERVER['REQUEST_METHOD']) && $_SERVER['REQUEST_METHOD'] !== 'POST') {
                if ( function_exists( 'status_header' ) ) {
                    status_header( 405 ); // WP #20986
                    header( 'Allow: POST' );
                }
                header('Content-Type: text/plain'); // merged from WP #9093
                die('XML-RPC server accepts POST requests only.');
            }

            global $HTTP_RAW_POST_DATA;
            if (empty($HTTP_RAW_POST_DATA)) {
                // workaround for a bug in PHP 5.2.2 - http://bugs.php.net/bug.php?id=41293
                $data = file_get_contents('php://input');
            } else {
                $data =& $HTTP_RAW_POST_DATA;
            }
        }
        $this->message = new IXR_Message($data);
        if (!$this->message->parse()) {
            $this->error(-32700, 'parse error. not well formed');
        }
        if ($this->message->messageType != 'methodCall') {
            $this->error(-32600, 'server error. invalid xml-rpc. not conforming to spec. Request must be a methodCall');
        }
        $result = $this->call($this->message->methodName, $this->message->params);

        // Is the result an error?
        if (is_a($result, 'IXR_Error')) {
            $this->error($result);
        }

        // Encode the result
        $r = new IXR_Value($result);
        $resultxml = $r->getXml();

        // Create the XML
        $xml = <<<EOD
<methodResponse>
  <params>
    <param>
      <value>
      $resultxml
      </value>
    </param>
  </params>
</methodResponse>

EOD;
      // Send it
      $this->output($xml);
    }