CURLOPT_PROXY_KEYPASSWD

CURLOPT_PROXY_KEYPASSWD is one of the accepted parameters for curl_setopt parameter #2.

CURLOPT_PROXY_KEYPASSWD — Set the string be used as the password required to use the CURLOPT_PROXY_SSLKEY private key. A passphrase is not needed to load a certificate but one is needed to load a private key. This option is for connecting to an HTTPS proxy, not an HTTPS server. Available as of PHP 7.3.0 and cURL 7.52.0.

CURLOPT_PROXY_KEYPASSWD = 10258;