问调用鉴黄接口为什么返回'message' => 'response is not json: '？

调用：var_dump ($client->pornDetect(array('urls'=>array('http://img3.a0bi.com/upload/ttq/20160814/1471155260063.png',
"http://jiangsu.china.com.cn/uploadfile/2015/1102/1446443026382534.jpg")))); 

返回：array (size=4)
  'code' => int -2
  'message' => string 'response is not json: ' (length=22)
  'httpcode' => int 0
  'data' => 
    array (size=0)
      empty