Here is an sample how to create valid X.509 Public and Private Key (cert/key).
When not using self signed the 4.2.1 segault. You need the CVS code at least for openssl.
<?
Header("Content-Type: text/plain");
$CA_CERT = "CA.cert.pem";
$CA_KEY  = "CA.key.pem";
$req_key = openssl_pkey_new();
if(openssl_pkey_export ($req_key, $out_key)) {
        $dn = array(
                "countryName"            => "DE",
                "stateOrProvinceName"    => "Frankfurt",
                "organizationName"       => "smcc.net",
                "organizationalUnitName" => "E-Mail",
                "commonName"             => "Testcert"
                );
        $req_csr  = openssl_csr_new ($dn, $req_key);
        $req_cert = openssl_csr_sign($req_csr, "file://$CA_CERT", "file://$CA_KEY", 365);
        if(openssl_x509_export ($req_cert, $out_cert)) {
                echo "$out_key\n";
                echo "$out_cert\n";
                }
        else    echo "Failed Cert\n";
        }
else            echo "FailedKey\n";
?>