Executing function before every controller request

I'm calling cloud APIs using token authentication with php-openstack-sdk.

$openstack = new OpenStack\OpenStack([
    'authUrl' => '{authUrl}',
    'region' => '{region}',
    'user' => [
        'id' => '{userId}',
        'password' => '{password}'
    ],
    'scope' => ['project' => ['id' => '{projectId}']]
]);

However, every API call requires me to be authenticated (as shown in the code above). Instead of repeating the same auth code in every controller function, how do I do it once and be able to call $openstack in my controller's functions? i.e., in my controller, I can directly use $openstack.

public function listServers() 
{
    $openstack->computeV2()->listServers();
}

Write the logic in the __construct() of your Controller.php if you want that to be accessible for all the controllers. If not, write the __construct() within the controller you need.

Controller.php

class Controller extends BaseController
{
    protected $openstack;

    public function __construct()
    {
        $this->openstack = new OpenStack\OpenStack([
            ...
        ]);
    }
}

NetworkController.php

class NetworkController extends Controller
{
    public function getNetworkDetails() {
        $network = $this->openstack->networking();
    }
}