Error code 401 when create a google slide API on Laravel

I'm studying google slide API on laravel framework now. i want to create a simple template at first but i stuck. i got this error.

> { "error": { "code": 401, "message": "Request is missing required authentication credential. Expected OAuth 2 access token, login cookie or other valid authentication credential. See https://developers.google.com/identity/sign-in/web/devconsole-project.", "errors": [ { "message": "Login Required.", "domain": "global", "reason": "required", "location": "Authorization", "locationType": "header" } ], "status": "UNAUTHENTICATED", "details": [ { "@type": "type.googleapis.com/google.rpc.ErrorInfo", "reason": "CREDENTIALS_MISSING", "domain": "googleapis.com", "metadata": { "service": "slides.googleapis.com", "method": "google.apps.slides.v1.PresentationsService.CreatePresentation" } } ] } }

I've been following the tutorial to obtain the OAuth credential with file .json on https://console.cloud.google.com and store it to folder "storage > app" folder

> {"web":{"client_id":"xxx.apps.googleusercontent.com","project_id":"xxx","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_secret":"xxx","redirect_uris":["mydomain"],"javascript_origins":["mydomain"]}}

and here is my code

<?php
namespace App\Http\Controllers;
use Google\Client as GoogleClient;
use Google\Service\Slides;
use Google\Service\Slides\BatchUpdatePresentationRequest;
use Google\Service\Slides\Presentation;
use Google\Service\Slides\CreateSlideRequest;
use Google\Service\Slides\LayoutPlaceholderIdMapping;
use Google\Service\Slides\InsertTextRequest;
class SlideController extends Controller
{
public function index()
{
$credentialsPath = storage_path('app/slide-api-credential.json');
$client = new GoogleClient();
$client->setAuthConfig($credentialsPath);
$client->addScope('Slides::PRESENTATIONS');
$slides = new Slides($client);
$presentation = new Presentation([
'title' => 'My First Slide'
]);
$slideRequests = [
new CreateSlideRequest([
'slideLayoutReference' => [
'predefinedLayout' => 'BLANK'
],
'placeholderIdMappings' => [
new LayoutPlaceholderIdMapping([
'objectId' => 'TITLE',
'layoutPlaceholder' => [
'type' => 'TITLE'
]
]),
new LayoutPlaceholderIdMapping([
'objectId' => 'SUBTITLE',
'layoutPlaceholder' => [
'type' => 'SUBTITLE'
]
])
]
]),
new InsertTextRequest([
'objectId' => 'TITLE',
'text' => 'Hello,'
]),
new InsertTextRequest([
'objectId' => 'SUBTITLE',
'text' => 'World!'
])
];
$batchUpdateRequest = new BatchUpdatePresentationRequest([
'requests' => $slideRequests
]);
$createdPresentation = $slides->presentations->create($presentation);
$presentationId = $createdPresentation->presentationId;
$slides->presentations->batchUpdate($presentationId, $batchUpdateRequest);
return "Slide created with ID: $presentationId";
}
}

just create a simple presentation slide. How do i able to solve this? please help

To make API calls to the Google Slides API you'll need to provide an authentication method, normally an Access Token, the slide-api-credential.json file is used to link your App to your Google Cloud Project in order to use the enabled APIs.

Your next step would be #2 from their documentation:

>Before your application can access private data using a Google API, it must obtain an access token that grants access to that API.

Maybe this could help you get in the right direction, I used this example from their Github repository in order to create a version of your code that would take the user through verification, save the token and use it to call the API:

public function index()
{
/********* Generating the Client and OAuthToken ******************/
$redirect_uri = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
$client = new GoogleClient();
$client->setScopes('Slides::PRESENTATIONS');
$client->setAuthConfig('app/slide-api-credential.json');
$client->setRedirectUri($redirect_uri);
$client->setAccessType('offline');
$client->setPrompt('select_account consent');
// Load previously authorized token from a file, if it exists.
// The file token.json stores the user's access and refresh tokens, and is
// created automatically when the authorization flow completes for the first
// time.
$tokenPath = 'token.json';
if (file_exists($tokenPath)) {
$accessToken = json_decode(file_get_contents($tokenPath), true);
$client->setAccessToken($accessToken);
}
// If there is no previous token or it's expired.
if ($client->isAccessTokenExpired()) {
// Refresh the token if possible, else fetch a new one.
if ($client->getRefreshToken()) {
$client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
} else {
// Request authorization from the user.
$authUrl = $client->createAuthUrl();
header('Location:' . $authUrl);
if (isset($_GET['code'])) {
$accessToken = $client->fetchAccessTokenWithAuthCode($_GET['code'], $_SESSION['code_verifier']);
$client->setAccessToken($accessToken);
// redirect back to the example
header('Location: ' . filter_var($redirect_uri, FILTER_SANITIZE_URL));
$client->setAccessToken($accessToken);
}
}
// Save the token to a file.
if (!file_exists(dirname($tokenPath))) {
mkdir(dirname($tokenPath), 0700, true);
}
file_put_contents($tokenPath, json_encode($client->getAccessToken()));
}
/******** End of Authorization Flow *********/
$slides = new Slides($client);
$presentation = new Presentation([
'title' => 'My First Slide'
]);
...

More documentation:

• Using OAuth 2.0 to Access Google APIs - General guide

• Google APIs Client Library for PHP - Examples

• Google APIs Client Library for PHP - Github Repo