/* If 1 package belonging to user */
elseif (count((array)$packageIds) === 1)
{
  $packageId = (array)$packageIds;
  $package = $this->model->find($packageId['0']);
}

This is your problem. With this case, your package is not an array, it's an Eloquent object.

This should fix it:

/* If 1 package belonging to user */
elseif (count((array)$packageIds) === 1)
{
  $packageId = (array)$packageIds;
  $package = array($this->model->find($packageId['0']));
}

And so to the case 0 package id, it should be returns as an array

OK, I've just take a closer look at your script. I wonder why you have to do the array casting ? Is this a better way?

/**
 * Get the package/s belonging to a certain user
 * @param int $packageIds
 * @return Object (StdClass)
*/
public function getPackageByUserId(array $packageIds)
{

$packages = array();

/* If no packages belonging to user */
if (count($packageIds) < 1)
{
  $packages[] = $this->createEmptyObject('package', $this->model->table);
}

/* If 1 package belonging to user */
elseif (count($packageIds) === 1)
{
  
  $packages[] = $this->model->find($packageId['0']);
}

/* If more than one package belonging to user */
if (count($packageIds) > 1)
{
  foreach ($packageIds as $packageId)
  {
    $packages[] = $this->model->find($packageId);
  }
}

return $packages; // Is returning array ok ?
}

OH!! Anotherthing, is this script do a Database query ?

$this->model->find($packageId);

If that, in the case with multiple ids, it's a query in a for loop and may harmful to your application's performance. It should do some thing like:

// One query, and you get all the package here, not in the for loop
$this->model->findAllByIds($packageIds);