/**
* 返回Json数据 * @param int $code * @param string $message 
* @param array $data * @return string 
*/
public function retJson($code,$message = '',$data = array()){    if(!is_numeric($code))    {  
      return '';    
}    
$result=array( 
       'code' => $code,     
   'message' => $message;    
    'data' => $data   
 );  
  echo json_encode($result); 
   exit;
}