<?php

$array = array(

  "Hello", // Level 1

  array(

    "World" // Level 2

  ),

  array(

    "How", // Level 2

    array(

      "are", // Level 3

      "you" // Level 3

    )

  ),

  "doing?" // Level 1

);

$recursiveIterator = new RecursiveArrayIterator($array);

$recursiveIteratorIterator = new RecursiveIteratorIterator($recursiveIterator);

foreach ($recursiveIteratorIterator as $key => $value) {

  echo "Depth: " . $recursiveIteratorIterator->getDepth() . PHP_EOL;

  echo "Key: " . $key . PHP_EOL;

  echo "Value: " .$value . PHP_EOL;

}

?>