(PHP Extension) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

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<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$dkim = new CkDkim();

// To create a DKIM signature for email (i.e. MIME),
// you'll need to provide the following:
// (1) An RSA private key in any common file format.
// (2) The domain name (typically the same domain
// as the sender of an email).
// (3) A selector for the domain name -- an arbitrary string
// to identify the matching public key in DNS.

// To allow an email recipient to verify the DKIM signature via an
// external email client supporting DKIM or using other software,
// you will need to create a DNS record with the selector
// and matching public key.  This example does not provide
// information about DKIM DNS record creation.  
// (Chilkat does not provide an API for creating DNS records.  
// Creating the DKIM DNS record is something you would do
// manually.)

// Set the domain and selector:
// You'll need to provide your own values here..
$dkim->put_DkimDomain('chilkatsoft.com');
$dkim->put_DkimSelector('tuna');

// Load a private key from any common RSA private key
// format, such as DER, PKCS8, PEM, XML, etc.
// The LoadDkimPkFile method automatically detects
// the file format and reads it appropriately.
// If a password is not required, you'll still need to provide
// a password string argument, but it is ignored.

$password = 'optionalPassword';
$privKey = new CkPrivateKey();
$success = $privKey->LoadAnyFormatFile('myPrivateKey.pem',$password);
if ($success != true) {
    print $privKey->lastErrorText() . "\n";
    exit;
}

$success = $dkim->SetDkimPrivateKey($privKey);
if ($success != true) {
    print $dkim->lastErrorText() . "\n";
    exit;
}

// Load a MIME file.
$mimeData = new CkByteData();
$success = $mimeData->loadFile('testMessage.eml');
if ($success != true) {
    print 'Failed to load file.' . "\n";
    exit;
}

// Sign it.  This adds the DKIM-Signature header and
// returns the new MIME with DKIM-Signature added.
$dkimSignedMime = new CkByteData();
$success = $dkim->AddDkimSignature($mimeData,$dkimSignedMime);
if ($success != true) {
    print $dkim->lastErrorText() . "\n";
    exit;
}

$success = $dkimSignedMime->saveFile('dkimSigned.eml');
if ($success != true) {
    print 'Failed to save file.' . "\n";
    exit;
}

print 'Success.' . "\n";

?>