How to pass array in Custom validation in Laravel 5.5

I have pass array booking_type_all parameter in custom validation it's given error "Array to string conversion". How to pass array.

$validatedData = Validator::make($request->all(),[
            'couponcode' => 'validcoupon:$request->booking_type_all,
        ]);

array booking_type_all:

array:1 [
  "TOURS" => array:1 [
    0 => "99848892-8617-41b9-808c-c44ca529d4e1"
  ],
  "VEHICLE" => array:1 [
    0 => "99848892-8617-41b9-808c-c44ca529d4e2"
  ]
]

via Chebli Mohamed