administraCursos/app/Http/Middleware/SetDept.php

<?php

namespace App\Http\Middleware;

use Closure;

class SetDept
{
    /**
     * Sets the department session variable to the desired department id or the default if none is set.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        if ($request->has('setdept')) {
            $data = $request->validate(['setdept' => 'integer|exists:departments,id']);
            $request->session()->put('department', $data['setdept']);
        }
        if (!$request->session()->has('department')) {
            $default_dept_id = \App\Department::whereNull('name')->first()->id;
            $request->session()->put('department', $default_dept_id);
        }
        // dump($request->session()->get('department'));
        return $next($request);
    }
}