Google specifies the metadata in https://developers.google.com/drive/api/v3/reference/files#resource.
If I do
$parameters['fields']="*";
$files = $service->files->listFiles($parameters);
Then I indeed get pretty much all that. If I just do
$files = $service->files->listFiles($parameters);
i.e. no fields setting I get a subset, but some fields such as createdTime are now blank - and that is one I need. Google recommend (https://developers.google.com/drive/api/v3/fields-parameter) listing only the fields you need to improve performance, but just about everything I put in fields gets an error "Invalid field selection" (tested in https://developers.google.com/drive/api/v3/reference/about/get?apix_params=%7B%22fields%22%3A%22createdTime%22%7D)
$parameters['fields']="name,parents,mimeType,filesize,createdTime,modifiedTime";
$files = $service->files->listFiles($parameters);
Any clues as to how this works? Thanks