PHP返回JSON和XML类

<?php
    class Reponse{
        //private $result = array('code'=null,'message'=null,'data'=>null);
        /**
         * @desc 返回JSON格式
         * @param int $code 
         * @param string $message 
         * @param array  $data
         * return string
         */
        public static function json($code,$message = null,$data = array()){
            if(!is_numeric($code)){
                return false;
            }
            $result = array(
                'code'=>$code,
                'message'=>$message,
                'data'=>$data
            );
            return json_encode($result);
            exit;
        }
        
        /**
         * @desc 返回xml格式数据
         * @parma int $code 状态码
         * @param string $message 提示
         * @param array $data 数据
         * return string 
         */
         public static function xml($code,$message = '',$data = array()){
            if(!is_numeric($code)){
                return false;
            }
            $result = array(
                'code'=>$code,
                'message'=>$message,
                'data'=>$data
            );
            $xml = '';
            
            $xml .= "<?xml version='1.0' encoding='UTF-8'?>
";
            $xml .= "<root>
";
            $xml .= self::xmlEncode($result);
            $xml .= "</root>";
            header("Content-Type:text/xml");
            echo $xml;

         }
         
         public static function xmlEncode($result){
            $xml = $attr ='';
            foreach($result as $key=>$val){
                if(is_numeric($key)){
                    $attr = "id='{$key}'";
                    $key = "item{$key}";
                }
                $xml .= "<{$key} {$attr}>";
                
                $xml .= is_array($val) ? self::xmlEncode($val) : $val;
            
                $xml .= "</{$key}>
";
            }
         
            return $xml;
         
         }
         
    }
    
    $data = array(
        'id'=>1,
        'age'=>20,
        'username'=>'tim',
        'others'=>array(1,2,3),
    );
    Reponse::xml(200,'success',$data);
    Reponse::json(200,'success',$data);