Laravel 5.6 - ErrorException (E_NOTICE) Undefined variable: photo

I read other questions but I don't find my answer.
And my problem:

ErrorException (E_NOTICE) Undefined variable: photo

my controller:

public function show($zip, $street)
    {
        Banner::locatedAt($zip, $street)->addPhoto($photo);
        return view('banners.show', compact('banner'));
    }

and addPhoto function on my model:

public function addPhoto(Photo $photo)
    {
        return $this->photos()->save($photo);
    }

Thank for your help

via Chebli Mohamed