How to redirect back to form with input - Laravel 5

You can use the following:

return Redirect::back()->withInput(Input::all());

If you're using Form Request Validation, this is exactly how Laravel will redirect you back with errors and the given input.

Excerpt from \Illuminate\Foundation\Validation\ValidatesRequests:

return redirect()->to($this->getRedirectUrl())
                    ->withInput($request->input())
                    ->withErrors($errors, $this->errorBag());

write old function on your fields value for example

<input type="text" name="username" value="{{ old('username') }}">