CURL error (58): Unable to install private key file: '/var/www/work/xml/keys/client.pem' PEM type

I am getting this error when connecting to the server using private and public keys.

CURL error (58): Unable to install private key file: '/var/www/work/xml/keys/client.pem' PEM type

My private keys contain both a key and a certificate. It also has a password.

My current code is here:

    $url="https://example.website.com";

    $pemfile = "/var/www/work/xml/keys/server.pem";
    $keyfile = "/var/www/work/xml/keys/client.pem";

    $requestXml = file_get_contents("net.xml");

    $ch = curl_init(); 
    curl_setopt($ch, CURLOPT_URL, $url); 
    curl_setopt($ch, CURLOPT_HTTP_VERSION, 1.1); 
    curl_setopt($ch, CURLOPT_PORT, 443); 
    curl_setopt($ch, CURLOPT_PROTOCOLS, CURLPROTO_HTTPS);

    curl_setopt($ch, CURLOPT_VERBOSE, 1); 
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE); 
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0); 

    curl_setopt($ch, CURLOPT_FAILONERROR, 0); 

    curl_setopt($ch, CURLOPT_SSLCERT, $pemfile); 
    curl_setopt($ch, CURLOPT_SSLCERTTYPE, 'PEM'); 
    curl_setopt($ch, CURLOPT_SSLCERTPASSWD, 'PASSWORD'); 


    curl_setopt($ch, CURLOPT_SSLKEY, $keyfile); 
    curl_setopt($ch, CURLOPT_SSLKEYPASSWD, "PASSWORD");


    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: text/xml'));
    curl_setopt($ch, CURLOPT_POSTFIELDS, $requestXml);

    $data = curl_exec($ch);
    $curl_errno = curl_errno($ch);
    $curl_error = curl_error($ch);

    if ($curl_errno > 0) 
    {
        echo "cURL Error ($curl_errno): $curl_error\n";
    }
    else 
    {
        header("Content-Type: text/xml");
        print_r($data);
    }

    curl_close($ch);