The collection classes provide a set of tools to manipulate arrays or Traversable objects. If you have ever used underscore.js, you have an idea of what you can expect from the collection classes.

Collections can be created using an array or Traversable object. A simple use of a Collection would be:

use Cake\Collection\Collection;

$items = ['a' => 1, 'b' => 2, 'c' => 3];
$collection = new Collection($items);

// Create a new collection containing elements
// with a value greater than one.
$overOne = $collection->filter(function ($value, $key, $iterator) {
    return $value > 1;
});

The Collection\CollectionTrait allows you to integrate collection-like features into any Traversable object you have in your application as well.

Please make sure you check the official documentation