Permanent authorization token Google API Sheets for php - php

Question

I'm working on a project where you need to use Google Api for Google Sheets service to make changes by means of php, but my access token obtained through clicking on the authorization link , lives only 2 hours. The problem is to extend the validity of the token for more than 2 hours, please help with this task.The following is an example of my function to get a Google client:
$client = new Google_Client();
$client->setApplicationName('My Project 45639');
//$client->setScopes(Google_Service_Sheets::SPREADSHEETS);
$client->setAuthConfig('credentials.json');
$client->setAccessType('offline');
$client->setPrompt('select_account consent');
$client->setScopes('https://www.googleapis.com/auth/spreadsheets');
// 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();
//printf("%s", $authUrl);
$authCode = trim('4/aQHXC2H_MmBA3ifDlXmJiDHyEk2m2QCoKrP1YDdAbBZSZBPUMmbINxg');
// Exchange authorization code for an access token.
$accessToken = $client->fetchAccessTokenWithAuthCode($authCode);
$client->setAccessToken($accessToken);
// Check to see if there was an error.
if (array_key_exists('error', $accessToken)) {
throw new Exception(join(', ', $accessToken));
}
}
// Save the token to a file.
if (!file_exists(dirname($tokenPath))) {
mkdir(dirname($tokenPath), 0700, true);
}
file_put_contents($tokenPath, json_encode($client->getAccessToken()));
}
return $client;