question

According to your description, I assume that you’ve finished this tutorial: https://docs.microsoft.com/en-us/gaming/playfab/features/multiplayer/photon/quickstart. You need each room’s PlayFab IDs, the first thing you need to do is to set PlayFabID as UserID by setting AuthenticationValues.UserId before Clients connect to photon server. After this operation, the “UserId” in ActorList will be the “PlayFabID”. When you need to get the PlayFabIDs, call Photon.Hive.Plugin.SerializableGameState.ActorList API to get the Actorlist which contains a list of all actors inside the room, parse each PlayFabID into an array, then you get all the PlayFabIds in each room.

By the way, Shared Group Data might worth a try. In each room event handler, update the PlayFabIDs into Shared Group Data for each player in the room to access. Here is the doc you may want to refer: https://docs.microsoft.com/en-us/gaming/playfab/features/social/groups/using-shared-group-data