string(258) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%8F%98%E5%8A%A8%E6%88%90%E6%9C%AC%E7%9A%84%E5%85%AC%E5%BC%8F%E6%98%AF%E4%BB%80%E4%B9%88 => Failed to connect to 125.88.227.171 port 38062: Connection refused"
变动成本的公式是什么
