PHP Extension

OAuth2 for a GMail using a JSON Service Account Key

See more GMail SMTP/IMAP/POP Examples

This example shows how to obtain an OAuth2 access token for Gmail using a Google Service Account and a JSON private key. Once acquired, the access token can be used to send emails. Remember, upon token expiration, this process needs to be repeated to obtain a new token. Note: This procedure is specific to OAuth2 with Google Service Account keys. PHP Extension

<?php

include("chilkat.php");

$success = false;

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

// --------------------------------------------------------------------------------
// For a step-by-step guide for setting up your Google Workspace service account,
// see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
// --------------------------------------------------------------------------------

// First load the JSON key into a string.
$fac = new CkFileAccess();
$jsonKey = $fac->readEntireTextFile('qa_data/googleApi/chilkat25-b4214220e565.json','utf-8');
if ($fac->get_LastMethodSuccess() != true) {
    print $fac->lastErrorText() . "\n";
    exit;
}

// A Google service account JSON private key looks like this:

// {
//   "type": "service_account",
//   "project_id": "chilkat25",
//   "private_key_id": "b4214220f565881e19eeb97c2699bf5a0d1e3e0b",
//   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQ...NXcM=\n-----END PRIVATE KEY-----\n",
//   "client_email": "chilkatsvc@chilkat25.iam.gserviceaccount.com",
//   "client_id": "109122032928932715958",
//   "auth_uri": "https://accounts.google.com/o/oauth2/auth",
//   "token_uri": "https://oauth2.googleapis.com/token",
//   "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
//   "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/chilkatsvc%40chilkat25.iam.gserviceaccount.com",
//   "universe_domain": "googleapis.com"
// }

$gAuth = new CkAuthGoogle();
$gAuth->put_JsonKey($jsonKey);

// Specify a scope.
$gAuth->put_Scope('https://mail.google.com/');

// Request an access token that is valid for this many seconds.
$gAuth->put_ExpireNumSeconds(3600);

// When using a Google Workspace account with Gmail APIs, a service account can impersonate a user 
// via a process called domain-wide delegation � and the "sub" claim in the JWT is what enables this.
// Domain-wide delegation allows a Google Workspace administrator to authorize a service account to 
// act on behalf of any user in the domain, without user interaction.

// This is required for server-to-server access to user data � such as reading/sending Gmail from a background service.
// This is your company email address.
$gAuth->put_SubEmailAddress('info@chilkat.xyz');

// Connect to www.googleapis.com using TLS
$tlsSock = new CkSocket();
$success = $tlsSock->Connect('www.googleapis.com',443,true,5000);
if ($success != true) {
    print $tlsSock->lastErrorText() . "\n";
    exit;
}

// Send the request to obtain the access token.
$success = $gAuth->ObtainAccessToken($tlsSock);
if ($success != true) {
    print $gAuth->lastErrorText() . "\n";
    exit;
}

// Examine the access token:
$accessToken = $gAuth->accessToken();
print 'Access Token: ' . $accessToken . "\n";

// Sample output:
// ya29.a0AW4XtxjGTD67Z8 .... IRw0218

// The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

// -----------------------------------------------------------------------
$mailman = new CkMailMan();

// Set the properties for the GMail SMTP server:
$mailman->put_SmtpHost('smtp.gmail.com');
$mailman->put_SmtpPort(587);
$mailman->put_StartTLS(true);

$mailman->put_SmtpUsername('info@chilkat.xyz');
$mailman->put_OAuth2AccessToken($accessToken);

// Create a new email object
$email = new CkEmail();

$email->put_Subject('This is a test');
$email->put_Body('This is a test');
$email->put_From('Chilkat Test <info@chilkat.xyz>');
$success = $email->AddTo('Chilkat Software','info@chilkatsoft.com');
// To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

$success = $mailman->SendEmail($email);
if ($success != true) {
    print $mailman->lastErrorText() . "\n";
    exit;
}

$success = $mailman->CloseSmtpConnection();
if ($success != true) {
    print 'Connection to SMTP server not closed cleanly.' . "\n";
}

print 'Successfully sent email using Gmail with a service account key.' . "\n";

?>