laravel facebook class not load only on controllers - php

Question

I'm trying to make a login system using facebook SDK, because later I'll need some user's data.
On my login page blade I put this code:
session_start();
...
$fb = new Facebook\Facebook([
'app_id' => 'Facebook_id',
'app_secret' => 'Facebook_secret',
'default_graph_version' => 'v2.2',
]);
$helper = $fb->getRedirectLoginHelper();
$permissions = ['email', 'user_likes']; // optional
$loginUrl = $helper->getLoginUrl("miwebsite.com/callback", $permissions);
OK. This works good.
Then I put this on my callback controller:
session_start();
$fb = new Facebook\Facebook([
'app_id' => 'Facebook_id',
'app_secret' => 'Facebook_secret',
'default_graph_version' => 'v2.2',
]);
$helper = $fb->getRedirectLoginHelper();
try {
$accessToken = $helper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
if (isset($accessToken)) {
// Logged in!
$_SESSION['facebook_access_token'] = (string) $accessToken;
echo $_SESSION['facebook_access_token'];
// Now you can redirect to another page and use the
// access token from $_SESSION['facebook_access_token']
}
And I get this error:
Class 'App\Facebook\Facebook' not found
But if I put the exact code (Copy-pasted) on the view (callback.blade.php) it works O_o
My question is. How can I fix it to work on the controller instead of the view? Because later I'm gonna need to retrieve some data and I need to make this works on controllers... :(
Any clue will help :)