php simpleXML添加CDATA格式数据

<?php 
/** 
* to show <title><![CDATA[Site Title]]></title>   instead of <title>Site Title</title> 
* 
*/ 
class SimpleXMLExtended extends SimpleXMLElement 
{ 
    public function addCData($cdata_text) 
    { 
        $node = dom_import_simplexml($this); 
        $no   = $node->ownerDocument; 
        $node->appendChild($no->createCDATASection($cdata_text)); 
    } 
}
$xmlFile    = &#39;config.xml&#39;; 
// instead of $xml = new SimpleXMLElement(&#39;<sites/>&#39;); 
$xml = new SimpleXMLExtended(&#39;<sites/>&#39;); 
$site = $xml->addChild(&#39;site&#39;); 
// instead of $site->addChild(&#39;site&#39;, &#39;Site Title&#39;); 
$site->title = NULL; // VERY IMPORTANT! We need a node where to append 
$site->title->addCData(&#39;Site Title&#39;); 
$site->title->addAttribute(&#39;lang&#39;, &#39;en&#39;); 
$xml->asXML($xmlFile);