Example use of IteratorAggregate interface to make a private array within the class iterable. Featuring gaming consoles because why not.

iterator_aggregate.php

<?php

/**
 * A class which contains a private list of gaming consoles.
 * Can be looped as the class implements IteratorAggregate
 *
 * Class ConsoleCollection
 */
class ConsoleCollection implements \IteratorAggregate
{
   private $consoles = [];

    public function getIterator()
    {
        return new ArrayIterator($this->consoles);
    }

    public function addConsole($console)
    {
        $this->consoles[] = $console;
    }

    public function getConsole($key)
    {
        if(isset($this->consoles[$key])) {
            return $this->consoles[$key];
        }
        return null;
    }
}

/**
 * Create a list of gaming consoles then loop it.
 */
$myCollection = new ConsoleCollection;
$myCollection->addConsole('Nintendo 64');
$myCollection->addConsole('Playstation 2');
$myCollection->addConsole('Neo Geo');

foreach ($myCollection as $console) {
    echo $console . PHP_EOL;
}