protected function xrdsContent()
    {
        $lines = array(
            '<?xml version="1.0" encoding="UTF-8"?>',
            '<xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">',
            '<XRD>',
            '    <Service>',
            '        <Type>' . $this->ns . '/' . ($this->select_id ? 'server' : 'signon') .'</Type>',
            '        <URI>' . $this->serverLocation . '</URI>',
            '    </Service>',
            '</XRD>',
            '</xrds:XRDS>'
            );
        return implode("\n", $lines);
    }