PHP group by similar value called by function

I have an element with title, type, description and so on. I have a DAO that defines all that and functions already created that extract the type for one element only: it’s getById().

How can I loop through all the elements and create groups of them by the same id?

$group = array();
foreach ($announcement as $announcements) {
    $announcementType = $this->getById($this->typeId());
}

I should put an "if" here, but I cannot understand how to "create a group for each elements with the same typeId".

>Solution :

It’s not clear why you cycle over $announcements, anyway you can try a solution like this:

$group = [];

foreach ($announcements as $announcement) {
   $id = $this->typeId();
   $group[$id][] = $this->getById($id);
}