CheckAdmin.php

<?php

namespace App\Http\Middleware;

use App\User;
use Closure;
use Illuminate\Support\Facades\Auth;

class CheckAdmin
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        if (Auth::check()) {
            /** @var User $user */
            $user = Auth::user();

            if ($user->isAdmin()) {
                return $next($request);
            }
        }

        return response()
            ->redirectToRoute('admin');
    }
}