Populating a multiple select value with previously selected values

Hello,

I currently have a select dropdown (multiple)

Here is how i display the select in the volt view file

 {{ select('inbox-user[]', getUsers, 'using': ['id_admin', 'name_admin'], 'multiple' : 'multiple', 'class' : 'form-control select2') }}

Then in the inboxController i pull the currently selected values from the database

$this->view->getUsers = AdminUser::find();

//get a list of all the users currently attached to this inbox
$users = AdminInboxes::find('id_inboxes = '.$row->getIdInbox());

foreach ($users as $user){
    $user_ids[] = $user->getIdAdmin();
}

So i end up with an array for $user_ids like this:

array(3) {
    [0]=>
    string(2) "26"
    [1]=>
    string(2) "28"
    [2]=>
    string(2) "29"
}

But when i run the query i get this error

phalcon Only scalar values can be assigned to UI components

Now if found a solution here:

How ever i dont understand how to apply that to my exampleas it doesnt reference the id of the selectbox in that example.Should it be something like this:

Phalcon\Forms\Element\Select()->setDefault(array([$user_ids]))

Or do i put the id of the select inside Select([$users_ids])

Any help very much appreciated, i am also open to doing it a different way as long as it works.

One other thing, i notice in the volt file i am using ['id_admin', 'name_admin'] but in the setDefault example i am just passing the array of Ids, do i also need to pass the name too?