Laravel登录获取NULL参数

我正在尝试laravel和php，但登录时遇到问题：

我的观点是：

      {{ Form::open('login', 'POST') , ['class' => 'navbar-form navbar-right'] }}
            <div class="form-group">
                {{ Form::text('username', Input::old('username'), ['class' => 'form-control']) }}
            </div>
            <div class="form-group">
             {{  Form::password('password', ['class' => 'form-control'])        }}
            </div>
            {{ Form::submit('Login', ['class' => 'btn btn-primary']) }}
            <a class="btn btn-success" href="../registrarse">registrarse</a>
{{ Form::close() }}

路线：

Route::post('/login', function(){
 $userdata = array(
        'username' => Input::get('username'),
        'password' => Input::get('password')
    );
    /* Try to authenticate the credentials */
    if(Auth::attempt($userdata)) 
    {
        // we are now logged in, go to admin
        return "oola";
    }
    else
    {
        return $userdata;
        return Redirect::to('registrarse');
    }});

我一直获得：

{"username":null,"password":null}

怎么了？