Illuminate\Contracts\Container\BindingResolutionException Target class [PostController] does not exist. code example

Example 1: Target class [] does not exist.

composer dump-autoload

Example 2: Illuminate\Contracts\Container\BindingResolutionException Target class [SlugController] does not exist.

Route::get('/test/{slug}',  'App\Http\Controllers\SlugController@show' );

Example 3: Illuminate\Contracts\Container\BindingResolutionException Target class [PagesController] does not exist.

Target class [PagesController] does not exist.