You can use yield from in getIterator in recent PHP 7 versions: 
<?php 
class Example implements \IteratorAggregate
{
 protected $data = [];
 public function __construct(array $data) 
 {
 $this->data = $data;
 }
 public function getIterator() 
 {
 yield from $this->data;
 }
}
$test = new Example([1, 2, 3]);
foreach ($test as $node) {
 echo $test, PHP_EOL;
}
/*
 * Outputs:
 *
 * 1
 * 2
 * 3 
 */ ?>