Iterating Over a Three-Dimensional Array in PHP

But to iterate over a three-dimensional array, three nested loops are needed. Let's say for example we have the following array:

php<?php
  $arr = [
    [
      ['a', 'b'],
      ['c', 'd'],
    ],
    [
      ['e', 'f'],
      ['g', 'h'],
    ],
    [
      ['i', 'j'],
      ['k', 'l'],
    ],
  ];
?>

Let's output all its elements to the screen:

php<?php
  foreach ($arr as $sub) {
    foreach ($sub as $subsub) {
      foreach ($subsub as $elem) {
        echo $elem;
      }
    }
  }
?>

php<?php
  $arr = [
    [
      [1, 2, 3],
      [6, 7, 8],
      [3, 8, 4],
      [6, 7, 9],
    ],
    [
      [9, 1, 2],
      [4, 5, 6],
    ],
    [
      [9, 1, 2],
      [4, 5, 6],
      [5, 6, 3],
    ],
  ];
?>