class PondsCollection implements IteratorAggregate
{
	private $collection = array();

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

	public function add($pond)
	{
		$this->collection[] = $pond;
	}
}


$ponds = new PondsCollection();
$ponds->add(...);

foreach ($ponds as $pond)
{
	...
}

//http://www.php.net/manual/en/class.iteratoraggregate.php
//http://www.php.net/manual/en/spl.iterators.php