这确实是openSSL中的一个bug。此功能仅在以下情况下有用：
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
另请参阅：
If no peer certificate was presented, the returned result code is X509_V_OK. This is because no verification error occurred, it does however not indicate success. SSL_get_verify_result() is only useful in connection with SSL_get_peer_certificate(3).
http://www.openssl.org/docs/ssl/SSL_get_verify_result.html#bugs
请记住，当您希望cURL连接到SSL并验证证书时，您必须先下载CA证书并将其保存到您的应用程序中（firefox可以做到这一点），然后在cURL调用中引用它。例如：

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
curl_setopt($ch, CURLOPT_CAINFO, getcwd() . "/CACertificats/AddTrustExternalCARoot.crt");

关于这点的小教程：http://unitstep.net/blog/2009/05/05/using-curl-in-php-to-access-https-ssltls-protected-sites/