/**
* 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' => $data
);
return json_encode($result);
}