GoogleAnalyticsController.php

<?php
public function get_tokens() {
	$google_client = new Google_Client();
	$google_client->setAuthConfig(ROOT . '/mbcms_config/client_secrets.json');
	$google_client->setAccessType("offline");
	$google_client->addScope(Google_Service_Analytics::ANALYTICS_READONLY);

	$tokens = $this->GoogleAnalytic->find(
		'list',
		array(
			'fields' => array(
				'name', 'value'
			)
		)
	);

	$tokens['tokens'] = json_decode($tokens['tokens'], true);

	$google_client->setAccessToken($tokens['tokens']);

	if($google_client->isAccessTokenExpired()) {
		$tokens['tokens']['refresh_token'] = $tokens['refresh_token'];
		$google_client->setAccessToken($tokens['tokens']);

		$google_client->fetchAccessTokenWithRefreshToken($google_client->getRefreshToken());

		$new_tokens = json_encode($google_client->getAccessToken(), true);

		$db = $this->GoogleAnalytic->getDataSource();
		$this->GoogleAnalytic->updateAll(
			array('value' => $db->value($new_tokens, 'string')),
			array('name' => 'tokens')
		);

		$tokens['tokens'] = json_decode($new_tokens, true);
	}

	return $tokens;
}