change synthax to php 7.2

public function getAppointment(Request $request) {

    $getAppointment = Appointment::with('gymClients', 'merchant', 'gymClientPurchase', 'gymClientPurchase.gymMembership')
        ->when($request->id, function ($builder) use ($request) {
            return $builder->where('id', $request->id);
        })
        ->when($request->category, function ($builder) use ($request) {
            return $builder->where('category', $request->category);
        })
        ->when($request->client_id, function ($builder) use ($request) {
            return $builder->where('client_id', $request->client_id);
        })
        ->when($request->merchant_id, function ($builder) use ($request) {
            return $builder->where('merchant_id', $request->merchant_id);
        })
        ->when($request->status, function ($builder) use ($request) {
            return $builder->where('status', $request->status);
        })
        ->when($request->membership_id, fn ($builder) => $builder->whereHas(
                'gymClientPurchase', fn ($builder) => $builder->where('membership_id', $request->membership_id)))
        ->get();

            $getAppointment = collect($getAppointment)->map(function ($getAppointment) {
                return (object)$getAppointment;
            });
            return $this->showAll($getAppointment);

}

please can anyone change the synthax in the membership_id to php 7.2 synthax . i tried and can't do it