Here is my controller:

<?php

namespace App\Http\Controllers\Api;

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

class RegisterController extends Controller
{
    public function register(Request $request)
    {
        dd('aa');
    }
}

As seen in the screenshot, the class exists and is in the correct place:

My api.php route:

Route::get('register', 'Api\RegisterController@register');

When I hit my register route using Postman, it gave me the following error:

Target class [Api\RegisterController] does not exist.

Update:

Thanks to the answer, I was able to fix it. I decided to use the fully qualified class name for this route, but there are other options as described in the answer.

Route::get('register', 'App\Http\Controllers\Api\RegisterController@register');

• Yes in laravel 8 this error is occur..
• After try many solutions I got these perfect solution
• Just follow the steps...

CASE - 1

We can change in api.php and in web.php files like below..
The current way we write syntax is

Route::get('login', 'LoginController@login');

should be changed to

Route::get('login', [LoginController::class, 'login']);

CASE - 2

1. First go to the file: app > Providers > RouteServiceProvider.php
2. In that file replace the line
   protected $namespace = null; with protected $namespace = 'App\Http\Controllers';
3. Then After add line ->namespace($this->namespace) as shown in image..
   

in laravel-8 default remove namespace prefix so you can set old way in laravel-7 like:

in RouteServiceProvider.php add this variable

protected $namespace = 'App\Http\Controllers';

and update boot method

public function boot()
{
       $this->configureRateLimiting();

       $this->routes(function () {
            Route::middleware('web')
                ->namespace($this->namespace)
                ->group(base_path('routes/web.php'));

            Route::prefix('api')
                ->middleware('api')
                ->namespace($this->namespace)
                ->group(base_path('routes/api.php'));
        });
}

laravel 8 updated RouteServiceProvider and it affects route with string syntax, You can change it like above, but recommended way is using action syntax not using route with string syntax:

Route::get('register', 'Api\RegisterController@register');

Should be changed to:

Route::get('register', [RegisterController::class, 'register']);

In laravel 8 you just add your controller namespace in routes\web.php

use App\Http\Controllers\InvoiceController; // InvoiceController is controller name Route::get('invoice',[InvoiceController::class, 'index']);

Or

go `app\Providers\RouteServiceProvider.php` path and remove comments

protected $namespace = 'App\\Http\\Controllers';

If you are using laravel 8

just copy and paste my code

use App\Http\Controllers\UserController;

Route::get('/user', [UserController::class, 'index']);

The Laravel 8 documentation actually answers this issue more succinctly and clearly than any of the answers here:

Routing Namespace Updates

In previous releases of Laravel, the RouteServiceProvider contained a $namespace property. This property's value would automatically be prefixed onto controller route definitions and calls to the action helper / URL::action method. In Laravel 8.x, this property is null by default. This means that no automatic namespace prefixing will be done by Laravel. Therefore, in new Laravel 8.x applications, controller route definitions should be defined using standard PHP callable syntax:

use App\Http\Controllers\UserController;

Route::get('/users', [UserController::class, 'index']);

Calls to the action related methods should use the same callable syntax:

action([UserController::class, 'index']);

return Redirect::action([UserController::class, 'index']);

If you prefer Laravel 7.x style controller route prefixing, you may simply add the $namespace property into your application's RouteServiceProvider.

There's no explanation as to why Taylor Otwell added this maddening gotcha, but I presume he had his reasons.

If you would like to continue using the original auto-prefixed controller routing, you can simply set the value of the $namespace property within your RouteServiceProvider and update the route registrations within the boot method to use the $namespace property:

class RouteServiceProvider extends ServiceProvider
{
    /**
     * This namespace is applied to your controller routes.
     *
     * In addition, it is set as the URL generator's root namespace.
     *
     * @var string
     */
    protected $namespace = 'App\Http\Controllers';

    /**
     * Define your route model bindings, pattern filters, etc.
     *
     * @return void
     */
    public function boot()
    {
        $this->configureRateLimiting();

        $this->routes(function () {
            Route::middleware('web')
                ->namespace($this->namespace)
                ->group(base_path('routes/web.php'));

            Route::prefix('api')
                ->middleware('api')
                ->namespace($this->namespace)
                ->group(base_path('routes/api.php'));
    });
}

In laravel-8 you can use like this

 Route::group(['namespace'=>'App\Http\Controllers', 'prefix'=>'admin',
 'as'=>'admin.','middleware'=>['auth:sanctum', 'verified']], function()
{
    Route::resource('/dashboard', 'DashboardController')->only([
        'index'
    ]);
});

Thanks

For solution just uncomment line 29:

**protected $namespace = 'App\\Http\\Controllers';**

in 'app\Providers\RouteServiceProvider.php' file.

just uncomment line 29

I got the same error when I installed Laravel version 8.27.0: The error is as follow:

But when I saw my app/Providers/RouteServiceProvider.php I have namespaces inside my boot method, then I just uncommented this => "protected $namespace = 'App\Http\Controllers';"

Now My Project is working:

Happened to me when I passing null to the middleware function

Route::middleware(null)->group(function () {
    Route::get('/some-path', [SomeController::class, 'search']);
});

Passing [] for no middleware works or probably just remove the middleware call if not using middleware :D

In case if you prefer grouping of this routes, you can do as :

Route::group(['namespace' => 'App\Http\Controllers\Api'], function () {
    Route::resource('user', 'UserController');
    Route::resource('book', 'BookController');
});

The way to define your routes in laravel 8 is either

// Using PHP callable syntax...
use App\Http\Controllers\HomeController;
Route::get('/', [HomeController::class, 'index']);

OR

// Using string syntax...
Route::get('/', 'App\Http\Controllers\HomeController@index');

A resource route becomes

// Using PHP callable syntax...
use App\Http\Controllers\HomeController;
Route::resource('/', HomeController::class);

This means that in laravel 8, there is no automatic controller declaration prefixing by default.

If you want to stick to the old way, then you need to add a namespace property in the app\Providers\RouteServiceProvider.php and activate in the routes method.

Follow this image instructions below:

On a freshly installed laravel 8, in the App/Providers/RouteServices.php

    * The path to the "home" route for your application.
 *
 * This is used by Laravel authentication to redirect users after login.
 *
 * @var string
 */
public const HOME = '/home';

/**
 * The controller namespace for the application.
 *
 * When present, controller route declarations will automatically be prefixed with this namespace.
 *
 * @var string|null
 */
// protected $namespace = 'App\\Http\\Controllers';

uncomment the

protected $namespace = 'App\Http\Controllers';

that should help you run laravel the old fashioned way.

Incase you are upgrading from lower versions of laravel to 8 then you might have to implicitly add the

protected $namespace = 'App\Http\Controllers';

in the RouteServices.php file for it to function the old way.

In this issue, I just do add namespace like below and it works

I got the same error when I installed Laravel version 8.27.0: The error is as follow:

But when I saw my app/Providers/RouteServiceProvider.php I have namespaces inside my boot method, then I just uncommented this => "protected $namespace = 'App\Http\Controllers';"

Now My Project is working:

Happened to me when I passing null to the middleware function

Route::middleware(null)->group(function () {
    Route::get('/some-path', [SomeController::class, 'search']);
});

Passing [] for no middleware works or probably just remove the middleware call if not using middleware :D

Just uncomment below line from RouteServiceProvider (If does not exists then add)

protected $namespace = 'App\\Http\\Controllers';

I had this error

(Illuminate\Contracts\Container\BindingResolutionException Target class [App\Http\Controllers\ControllerFileName] does not exist.

Solution: just check your class Name, it should be the exact same of your file name.

In Laravel 8 the way routes are specified has changed:

Route::resource('homes', HomeController::class)->names('home.index');