Send certificate.cer with curl request

I'm trying to send a .cer file with my curl request and something is just now working. I don't know if something is wrong with my code or what

if(file_exists( 'certificate.cer')) {
     curl_setopt($ch, curlopt_cainfo, 'certificate.cer'));
}

but I got CURL error 56

Level 34

@uniqueginun did you change your request to POST method like curl_setopt($ch, CURLOPT_POST,1);?

Level 9

yes. everything is ok except the part of certificate parameters. have you done it before because I'm stuck

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