What's wrong with where?

Question

Laravel

code:

if ($request->post('min_price'))
            $data->where('price','>=',$request->input('min-price'));

        if ($request->input('max_price'))
            $data->where('price','<=', $request->input('max-price'));

error: Illegal operator and value combination.
People, what's wrong?)
Is there something wrong with the data type?