Google TeamDrive getChildren of a teamDriveID PHP - php

Question

I'm using PHP and the following call to retrieve the top-level TeamDrive folders.
$service->teamdrives->listTeamdrives()->getTeamDrives();
Results
TeamDrive1 --- let's say the ID is XXXXXX
TeamDrive2 --- let's say the ID is YYYYYY
TeamDrive1 has a sub-folder called TeamDrive1Sub1 (ID is SSSSS)
then TeamDrive1Sub1 (ID PPPPP) also has a sub-folder etc
I've tried to use the Drive REST API files:List - but this does not seem to work...
I need to find the children "x" levels deep, how do I do that? Maybe some other interface call such as the one I'm using above $service->teamdrives->listTeamdrives()->getTeamDrives(); which allows me to start at the ID XXXXXX and retrieve it's children

Answer 1

Found my own answer, but there's probably a better way... if you have the ID of a teamdrive folder and want to get the sub-folders - here's what I have for the PHP code
//- first we need to get the $teamDriveId - using the /files/get & the $folderId we passed in
$folderId = "XXXXXX" // from above
$optParams = array(
'supportsTeamDrives' => true,
);
$results = $service->files->get($folderId, $optParams);
$teamDriveId = $results["teamDriveId"];
// now we can get the sub-folders (if there are any)
$params = [
'q' => "'{$folderId}' in parents and trashed = false and mimeType = 'application/vnd.google-apps.folder'",
'pageSize' => $pageSize,
'corpora' => 'teamDrive',
'includeTeamDriveItems' => true,
'supportsTeamDrives' => true,
'teamDriveId' => $teamDriveId, // this must be the parent Id
'orderBy' => 'name',
];
$results = $service->files->listFiles($params);
Hope this helps someone