and to iterate recursively use the (sparsely documented)  RecursiveArrayIterator

<?php

$fruits = array(
                "apple" => "yummy",
                "orange" => "ah ya, nice",
                "grape" => "wow, I love it!",
                 "plum" => "nah, not me"
                );

$veg = array("potato" => "chips", "carrot" => "soup");
$grocery = array($fruits, $veg);
$obj = new ArrayObject( $grocery );

$it = new RecursiveIteratorIterator( new RecursiveArrayIterator($grocery));

foreach ($it as $key=>$val)
echo $key.":".$val."\n";

?>

Output
--------
apple:yummy
orange:ah ya, nice
grape:wow, I love it!
plum:nah, not me
potato:chips
carrot:soup