You can easily realise that ArrayObject can use various functions as they are in ArrayIterator to iterate an object-as-a-array. However, you need to "activate" these function (rewind, valid, next and so on...) by using getIterator() first. Actually this function inherits from Iterator Aggregate interface.

Take a look at the following basic example. The results are the same:

<?php

$array = [1, 2, 3, 4];
$a = new ArrayObject($array);
$b = new ArrayIterator($array);

$iterator = $a->getIterator();

for($iterator->rewind(); $iterator->valid(); $iterator->next()){
    echo $iterator->current()*2;
    
}

for($b->rewind(); $b->valid(); $b->next()){
    echo $b->current()*2; 
    
}

//Resulst are the same 2468 AND 2468