PHP Curl Error 35 - Peer reports incompatible or unsupported protocol version

Question

I'm attempting to make POST requests to an external API(Code below). I manage to get the curl coding working on my localhost but when I go to my staging server the curl returns error Peer reports incompatible or unsupported protocol version(35) . From reading into this I need to add an error buffer to get more debugging info but the documentation is confusing.

Yet when I make a curl request directly in the servers terminal with I receive a connection successful. Which makes me extremely confused as the server is clearly capable to make curl requests.

PHP Curl Code

$curl = curl_init();

  curl_setopt_array($curl, array(
    CURLOPT_URL => $url,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_POSTFIELDS => json_encode($body),
    CURLOPT_HTTPHEADER => $header,
  ));

  $response = curl_exec($curl);
  $err = curl_error($curl);
  echo "response: " . $response;
  echo "<br><br>error: " . $err;

  curl_close($curl);

Server Curl Response curl https://support.zendesk.com/api/v2/users/create_or_update.json

* About to connect() to support.zendesk.com port 443 (#0)
*   Trying 104.16.51.111...
* Connected to support.zendesk.com (104.16.51.111) port 443 (#0)
* Initializing NSS with certpath: sql:/etc/pki/nssdb
*   CAfile: /etc/pki/tls/certs/ca-bundle.crt
  CApath: none
* SSL connection using TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
* Server certificate:
*   subject: CN= support.zendesk.com,O="CloudFlare, Inc.",L=San Francisco,ST=CA,C=US
*   start date: Mar 08 00:00:00 2019 GMT
*   expire date: Mar 08 12:00:00 2020 GMT
*   common name: support.zendesk.com
*   issuer: CN=CloudFlare Inc ECC CA-2,O="CloudFlare, Inc.",L=San Francisco,ST=CA,C=US
> GET /api/v2/users/create_or_update.json HTTP/1.1
> User-Agent: curl/7.29.0
> Host: support.zendesk.com
> Accept: */*
> 
< HTTP/1.1 401 Unauthorized
< Date: Fri, 12 Apr 2019 12:52:28 GMT
< Content-Type: application/json; charset=UTF-8
< Content-Length: 37
< Connection: keep-alive
< Set-Cookie: __cfduid=da0ecd56691c96b9b3dac091df58383d51555073548; expires=Sat, 11-Apr-20 12:52:28 GMT; path=/; domain=.ralphandrussoclientcare.zendesk.com; HttpOnly
< WWW-Authenticate: Basic realm="Web Password"
< Strict-Transport-Security: max-age=31536000;
< Cache-Control: no-cache
< X-Zendesk-Origin-Server: app23.pod17.euw1.zdsys.com
< X-Request-Id: 4c65566eacc82981-DUB
< X-Runtime: 0.032000
< X-Zendesk-Request-Id: 3360f95a861586e6f414
< Set-Cookie: __cfruid=7af98f1cbac97922c1c15b82f7c133c3945a446e-1555073548; path=/; domain=.ralphandrussoclientcare.zendesk.com; HttpOnly
< Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
< Server: cloudflare
< CF-RAY: 4c65566eacc82981-DUB
< 
* Connection #0 to host support.zendesk.com left intact
{"error":"Couldn't authenticate you"}

Answer 1

In order to solve this problem I performed a server SSL test using https://www.ssllabs.com/ssltest/ which showed me which Protocols were already open and available on the server.

From that I followed the answer to this question TLS 1.2 not working in cURL which showed me which PHP CURLOPT_SSLVERSION number to use in order to access an open protocol.

Therefore I had to add the following line of code to my Curl Array

CURLOPT_SSLVERSION => CURL_SSLVERSION_TLSv1_2