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//Some times this error comes when you forget the square bracket [] in you route in 'laravel >=8'
Route::get('/test', [controllerName::class, 'functionName']);
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use App\Http\Controllers\UserController;
Route::get('manageUser', UserManageController::class);
//change to as below
Route::resource('manageUser', UserManageController::class);
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Route::get('/projects', [User\ProjectController::class, 'index'])->name('user.projects');