Type Safe PHP Collection

PageCollection.php

<?php declare(strict_types=1);

use ArrayIterator;
use IteratorAggregate;
use Traversable;

class PageCollection implements IteratorAggregate
{
    /** @var Page[] */
    private $items;

    public function getIterator(): Traversable
    {
        return new ArrayIterator($this->items);
    }

    public function addPage(Page $page): void
    {
        $this->items[] = $page;
    }
}