データをXMLにカプセル化する方法について

<?php
xml方式封装数据方法
/**
 * [xmlEncode description]
 * @param  [type] $code    [description]
 * @param  [type] $message [description]
 * @param  array  $data    [description]
 * @return [type]          [description]
 */
public static function xmlEncode($code,$message,$data= array()){
    if(!is_numeric($code)){
        return;
    }    
    $result = array(
        &#39;code&#39;=>$code,
        &#39;message&#39;=>$message,
        &#39;data&#39;=>$data,
        );
    header("Content-Type:text/html");
    $xml ="<?xml version=&#39;1.0&#39; encoding=&#39;UTF-8&#39;>";
    $xml .="<root>";
    $xml .=self::xmlToEncode($result);
    $xml .="</root>";

 echo $xml;
}


public static function xmlToEncode($data){
    $xml = $attr "";
    foreach ($data as $key => $value) {
        //xml的节点不能为数字，如果传默认数组需要处理下标值
        if(is_numeric($key)){
            $attr = "id=&#39;{$key}&#39;";
            $key = "item";
        }
        $xml .="<{$key}>";    
        $xml .=is_array($value)?self::xmlToEncode($value):$value;    
        $xml .="</{$key}>";    
    }
    return $xml;

}
$data = array(
    &#39;id&#39;=>1,
    &#39;name&#39;=>&#39;xinlang&#39;,
    &#39;type&#39;=>array(),
    );
Response::xmlEncode(200,&#39;success&#39;,$data);


//注意 xml的节点不能为数字，如果传默认数组需要处理下标值
<item id="0"></item>