According to documentation: to verify host or peer certificate you need to specify alternate certificates with the CURLOPT_CAINFO option or a certificate directory can be specified with the CURLOPT_CAPATH option.
Also look at CURLOPT_SSL_VERIFYHOST:
1 to check the existence of a common name in the SSL peer certificate.
2 to check the existence of a common name and also verify that it matches the hostname provided.
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);