How to filter an array of object?

You can use array_filter with a custom callback:

function filter_callback($element) {
  if (isset($element->foo) && $element->foo == 'some_value') {
    return TRUE;
  }
  return FALSE;
}

$arr = array_filter($arr, 'filter_callback');

Want to filter an array? Use array_filter!

$new_array = array_filter($array, function($obj){
    if (isset($obj->admins)) {
        foreach ($obj->admins as $admin) {
            if ($admin->member == 11) return false;
        }
    }
    return true;
});