可以使用 echo curl_error($ch); 打印错误信息
如果是 SSL certificate problem, verify that the CA cert is OK 这种错误
在php.ini搜索curl.cainfo，改成这个值
curl.cainfo=”/etc/ssl/certs/ca-bundle.crt”
https://stackoverflow.com/questions/8227909/curl-exec-always-returns-false
https://stackoverflow.com/questions/6400300/https-and-ssl3-get-server-certificatecertificate-verify-failed-ca-is-ok