How to get current arena playlist stats

I’m using the Halo 5 API right now and I’m getting data from the API.
Right now I’m fetching Total Arena Kills like this:
$array[‘TotalKills’] = $playerStats->Results[0]->Result->ArenaStats->TotalKills;

witch works fine, but when I want to fetch a “Tier” for a player it gives me error:
$array[‘Tier’] = $playerStats->Results[0]->Result->ArenaStats->ArenaPlaylistStats->PlaylistId->HighestCsr->Tier;

How would I set up a users current seasons Team Arena Stats?
$array[‘Tier’] = $playerStats->Results[0]->Result->ArenaStatsPlaylistId[c98949ae-60a8-43dc-85d7-0feb0b92e719]->HighestCsr->Tier; ??? maybe something like this

// Team Arena Playlist ID: c98949ae-60a8-43dc-85d7-0feb0b92e719