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:
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);