How to append a number to syntax properly

quiz app,I am trying to access my choice0,choice1,choice2,choice3 named inputs. But i need to make my $request->choice be $request->choice1`` for the first one and$request->choice2``` for the second and same for choice3 and choice4. But this does not work, How would I be able to do this

public function update(Request $request, $id)
    {
        $question = Question::find($id);
        $question->question = $request->question;
        $i = 1;
        echo $request->choice1;

        foreach ($question->choice as $choice) {
            $choicestring = "choice".$i;
            echo $choicestring;
            $choice = $request->choicestring;
            dd($choice);
            $i++;
        }
    }

the first echo gives me the value of the requests choice1 correctly and the echo of $choicestring gives me the value "choice1" which is correct but when I use them combined in $choice I get null when I echo/dd it