Get Firestore access token for REST api with google-api-php lib

Question

I'm trying to get an access token to make REST calls to my Firestore DB. I'm using PHP (only way for now) and have taken the next steps:

• Created a service account in the Firebase console and downloaded the key JSON
• Downloaded the Google-api-php library from https://developers.google.com/api-client-library/php/ and included in my code

And created this code:

putenv('GOOGLE_APPLICATION_CREDENTIALS='.__DIR__ .'/key.json');
$client = new Google_Client();
$client->useApplicationDefaultCredentials();
$client->addScope('https://www.googleapis.com/auth/datastore,https://www.googleapis.com/auth/cloud-platform');
$client->authorize();

I also replaced the

$client->useApplicationDefaultCredentials();  

part with

$client->setAuthConfig(__DIR__ .'/key.json'); 

Now when I var_dump the $client, the token stays NULL.

I just can't figure out, how to get the access_token for my service account. Anybody an idea how I can get an access token?

Answer 1

1. If you want to add multiple scopes, you will have to use an array instead of a string. A string will only be treated as one single scope.

2. The $client->authorize() returns a Client instance which is authorized to to access the Google Services for the given scopes. So, $authorizedClient = $client->authorize(); would be more appropriate.

3. If you just want to retrieve the access token, you could use $client->fetchAccessTokenWithAssertion(), which would give you something like this:

   Array
   (
       [access_token] => ya29.c..............
       [token_type] => Bearer
       [expires_in] => 3600
       [created] => 1511280489
   )
   

Here is the complete script I used to test this:

<?php

require __DIR__.'/vendor/autoload.php';

$client = new Google_Client();
$client->useApplicationDefaultCredentials();
$client->addScope([
    'https://www.googleapis.com/auth/datastore',
    'https://www.googleapis.com/auth/cloud-platform'
]);
// $client->authorize();

print_r($client->fetchAccessTokenWithAssertion());