gistfile1.aw

<?php

class foo implements IteratorAggregate
{
    public $a;
    public $b;

    public function getIterator()
    {
        return new ArrayIterator(array('foo', 'bar'));
    }
}

$foo = new foo;

$props = array();

foreach($foo as $name => $value) {
    $props[$name] = true;
}

// $props is not foo's properties
var_dump($props);