- var_dump: documentation ( source)
<?php
$a1 = [1, 2, 3];
$a2 = [4, 7, 10];
$a3 = [5, 6, 8, 9];
$it1 = new ArrayIterator($a1);
$it2 = new ArrayIterator($a2);
$it3 = new ArrayIterator($a3);
$m = new ArrayIterator([$it1, $it2, $it3]);
foreach(new \RecursiveIteratorIterator($m) as $v) {
var_dump($v);
}