curl error 35 : unknown SSL protocol error in connection

try this

curl_setopt($ch, CURLOPT_SSLVERSION, CURL_SSLVERSION_SSLv3); // Force SSLv3 to fix Unknown SSL Protocol error

You can use --tlsv1 option to solve the issue in case the curl version is below 7.34

 curl -I --tlsv1 https://9.185.173.135

In my case on a AIX VM also this problem, use --cacert to specific a cacert.pem

curl --cacert /var/ssl/cacert.pem https://localhost:3000

To Rudi : Thanks for the hint, that tells me a hell lot of info.

Somehow the admin of the secured page "refreshes" the state of certifications every day. So although I got blocked from accessing it yesterday, it generously lets me to grab another certificate and add it to the exception list of Firefox.

So everything is working, and I really learn something from yesterday's experience.