如何在Laravel 8中存储多个选择值？

class Choice extends Model
{
    public function users()
    {
        return $this->belongsToMany(User::class, 'choice_user');
    }
}

Route::post('/choices', [ChoiceController::class, 'store']);

class ChoiceController extends Controller
{
    public function store(Request $request)
    {
        $choices = $request->input('choices');

        // 存储选择值
        $choice = new Choice;
        $choice->name = $choices['name'];
        $choice->save();

        // 关联用户
        $choice->users()->attach($choices['user_ids']);

        // 其他逻辑...

        return response()->json(['message' => '选择值存储成功']);
    }
}

<form id="choice-form">
    <input type="text" name="choices[name]" placeholder="选择值名称">
    <select name="choices[user_ids][]" multiple>
        <option value="1">用户1</option>
        <option value="2">用户2</option>
        <option value="3">用户3</option>
    </select>
    <button type="submit">提交</button>
</form>

$('#choice-form').submit(function(e) {
    e.preventDefault();

    var formData = $(this).serialize();

    $.ajax({
        url: '/choices',
        type: 'POST',
        data: formData,
        success: function(response) {
            console.log(response.message);
        }
    });
});