I have relationship many to many...whats right query to implement it knowing that my query contain if statement and paginate?

$guests = Guest::with('programs');
   // dd($guests);
        if ($request->session()->get('program_name') != -1)
        $guests->where('guest_fname', 'like' , '%' . $request->session()->get('search') . '%' )
        ->orderBy($request->session()->get('field'), $request->session()->get('sort'))
        ->whereHas('programs', function($q) use ($request){
            $q->where('program_name', $request->session()->get('program_name'));
    })->paginate(20);

whats right code to get data from DataBase?

via Chebli Mohamed