LARAVEL add Sortby Filter on Search results by using Select orderby rate desc

I can't add sorting select on my search result. I can't make it work. I've added if statement to sort by select statement like this:

//I've tried to add if statement to sort manually by selecting but, no results changing. // AM I MISSING SOMETHING OR HOW DO I FIX IT?

public function search(Request $request){
    $cityKey = $request->cityKey;
    $key = $request->key;


        $doctors = Doctor_list::where('speciality_title', 'LIKE', '%' . $key . '%')->
        where('location', 'LIKE', '%' . $cityKey . '%')->
        orWhere('doctors_name', 'LIKE', '%' . $key . '%')->
        where('location', 'LIKE', '%' . $cityKey . '%')->
        orWhere('speciality_type', 'LIKE', '%' . $key . '%')->
        where('location', 'LIKE', '%' . $cityKey . '%')->get();


    If ($request->get('sortBy') === 'rate'){
        dd($doctors->orderBy('rate', 'desc'));
    }
    return view('healthflex.search', compact('doctors'));
}

<select name="sortBy" class="select"> //THIS IS SELECT STATEMENT
    <option>choose</option>
    <option class="sorting" value="rate}">rate</option>
    <option class="sorting">Popular</option>
    <option class="sorting">Ohirgi</option>

via Chebli Mohamed