IXR_Message::tag_open

        // Grab the error messages, if any
        if ($this->messageType == 'fault') {
            $this->faultCode = $this->params[0]['faultCode'];
            $this->faultString = $this->params[0]['faultString'];
        }
        return true;
    }

    function tag_open($parser, $tag, $attr)
    {
        $this->_currentTagContents = '';
        $this->currentTag = $tag;
        switch($tag) {
            case 'methodCall':
            case 'methodResponse':
            case 'fault':
                $this->messageType = $tag;
                break;
                /* Deal with stacks of arrays and structs */
            case 'data':    // data is to all intents and puposes more interesting than array
                $this->_arraystructstypes[] = 'array';