Manage to make it work at last.
$dn = array(
"countryName" => "XX",
"stateOrProvinceName" => "Location",
"localityName" => "Local",
"organizationName" => "Sample Organization",
"organizationalUnitName" => "Organizational Unit",
"commonName" => "Sample",
"emailAddress" => "contactus@email.com"
);
// Generate a new private (and public) key pair
$privkey = openssl_pkey_new(array(
"private_key_bits" => 4096,
"private_key_type" => OPENSSL_KEYTYPE_RSA,
));
// Generate a certificate signing request
$csr = openssl_csr_new($dn, $privkey, array('digest_alg' => 'sha512'));
// Generate a self-signed cert, valid for 365 days
$x509 = openssl_csr_sign($csr, null, $privkey, $days=365, array('digest_alg' => 'sha512'));
// Save your private key, CSR and self-signed cert for later use
openssl_csr_export($csr, $csrout) and var_dump($csrout); // .csr
openssl_x509_export($x509, $certout) and var_dump($certout); // .crt.pem
openssl_pkey_export($privkey, $pkeyout, "user_defined_password") and var_dump($pkeyout); // .key.pem
if(openssl_cms_sign ( "file_to_sign", "Sample.p7m" , $x509 , $privkey, null , 0 , 0 , null )){
echo "SIGNED SUCCESSFULLY! Sample.p7m created... \r\n";
}
else
{
echo "SIGNED FAILED!\r\n";
}