Curl error with client certificate authentication - php

Question

I have to call an api that requires the client certificate authentication.
I test this api in postman with client certification and its working perfectly.
Now i want to do it with php curl.
I tried below code but its giving me following error.
HTTP/2 stream 0 was not closed cleanly: HTTP_1_1_REQUIRED (err 13)
$url = 'https://someurl';
$json = 'somejson';
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_VERBOSE, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, true);
curl_setopt($ch, CURLOPT_SSLCERT, __DIR__."/certificate.pem");
curl_setopt($ch, CURLOPT_SSLCERTTYPE, 'PEM');
curl_setopt($ch, CURLOPT_SSLKEY, __DIR__."/privatekey.key");
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
curl_setopt($ch, CURLOPT_POSTFIELDS, $json);
$responseData = curl_exec($ch);
if(curl_errno($ch)) {
echo curl_error($ch);
}
curl_close($ch);

Answer 1

The error message has all the clues you need: HTTP_1_1_REQUIRED
TLS client certificates are not supported for HTTP/2, so you need to make sure your curl request is done using HTTP/1.1 by explicitly asking for that. curl will by default upgrade to HTTP/2 on HTTPS URLs otherwise.
Set CURLOPT_HTTP_VERSION to CURL_HTTP_VERSION_1_1.