Some help with notifaiction files

Hi,

I try to notify members groups when a file is upload on group.

I do that but I don't unserstand one point -> How I can send list of members groups ? I use

$model = ES::model('Groups');

$targets = $model->getMembers($group->id, array('state' => SOCIAL_STATE_PUBLISHED));

but It seems don't working.
If $targets = ['421, '326'], I have notification.

Can you help me, I haven't find documentation about that.

I join my code. You can find it in row 454

Thank you