Internal Server Error: Class "App\Http\Controllers\URL" not found

This is a namespace related issue. When we want to URL class in our Laravel code, we should use following namespace:

use URL;

or

use Illuminate\Support\Facades\URL;

Example:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use Illuminate\Support\Facades\URL;

class TestController extends Controller
{
    protected $request;

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct(Request $request) {
        $this->request = $request;
    }

    public function index()
    {
        echo URL::to('/');
    }
}

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use URL;

class TestController extends Controller
{
    protected $request;

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct(Request $request) {
        $this->request = $request;
    }

    public function index()
    {
        echo URL::to('/');
    }
}