Determining If The Current User Is Authenticated
https://laravel.com/docs/5.4/authentication
<?php
/*
To determine if the user is already logged into your application, 
you may use the check method on the Auth facade, 
which will return true if the user is authenticated:
*/
use Illuminate\Support\Facades\Auth;
if (Auth::check()) {
    // The user is logged in...
}