(PHP Extension) Get Firebase Access Token from JSON Service Account Private Key

Demonstrates how to get a Firebase access token using a JSON service account private key. Your Firebase service account can be used to authenticate multiple Firebase features, such as Database, Storage and Auth, programmatically.

A Firebase JSON service account private key can be created in the Firebase settings/admin portion of the console.firebase.google.com site as shown here:

Scroll down to see the example code...

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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.

// First load the Firebase JSON private key into a string.
$fac = new CkFileAccess();
$jsonKey = $fac->readEntireTextFile('qa_data/firebase/firebase-chilkat-firebase-adminsdk-n28n4-1b664ee163.json','utf-8');
if ($fac->get_LastMethodSuccess() != true) {
    print $fac->lastErrorText() . "\n";
    exit;
}

// A Firebase JSON private key should look something like this:

// { 
//   "type": "service_account",
//   "project_id": "firebase-chilkat",
//   "private_key_id": "1c664ee164907413c91ddefcf5b765ecba8779e2",
//   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQIBA ... Ya2UZii/lXn73/ZOK8=\n-----END PRIVATE KEY-----\n",
//   "client_email": "firebase-adminsdk-n28n4@firebase-chilkat.iam.gserviceaccount.com",
//   "client_id": "134846322329335418431",
//   "auth_uri": "https://accounts.google.com/o/oauth2/auth",
//   "token_uri": "https://accounts.google.com/o/oauth2/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/firebase-adminsdk-n28n4%40firebase-chilkat.iam.gserviceaccount.com"
// } 
// 

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

// Choose a scope.
// The scope could be "https://www.googleapis.com/auth/firebase.database"
// or a space-delimited list of scopes:
// "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email"

$gAuth->put_Scope('https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email');

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

// If the application is requesting delegated access:
// The email address of the user for which the application is requesting delegated access,
// then set the email address here. (Otherwise leave it empty.)
$gAuth->put_SubEmailAddress('');

// Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
// The Chilkat socket object is used so that the connection can be established
// through proxies or an SSH tunnel if desired.
$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:
print 'Firebase Access Token: ' . $gAuth->accessToken() . "\n";

// Save the token to a file (or wherever desired).  This token is valid for 1 hour.
$fac->WriteEntireTextFile('qa_data/tokens/firebaseToken.txt',$gAuth->accessToken(),'utf-8',false);

?>