Yii2 Composer Library未在Component中加载

I'm using the Google PHP Library that I've installed via Composer.

"google/apiclient": "*"

I can run the test code in the view but when I try to run it in the Controller I get an error.

Class 'backend\controllers\Google_Client' not found

Here is the Test code

$client = new Google_Client();
$client->setApplicationName("Client_Library_Examples");
$client->setDeveloperKey("***********************");
$service = new Google_Service_Books($client);
$optParams = array('filter' => 'free-ebooks');
$results = $service->volumes->listVolumes('Henry David Thoreau', $optParams);

Class 'backend\controllers\Google_Client' not found

It seems like you didn't define namespace using.

use Google\Google_Client; //or somethong like this

If Google_Client hasn't namespace use require to import class from file

require \Yii::getAlias('common/components/simple_html_dom') . '.php';

I think Google_Client don't use namespaces. So use "\".

$client = new \Google_Client();