Imprimir arreglo recursivamente

<?php
  function imprimirarreglo($a) {
    echo '<blockquote>';
    foreach ($a as $key => $value) {
      echo htmlspecialchars("$key: ");
      if (is_array($value)) {
        imprimirarreglo($value);
      } else {
        echo htmlspecialchars($value) . '<br />';
      }
    }
    echo '</blockquote>';
  }

  $arr = array(
    'Roman' =>
      array('one' => 'I', 'two' => 'II', 'three' =>
        'III', 'four' => 'IV'),
    'Arabic' =>
      array('one' => '1', 'two' => '2', 'three' =>
        '3', 'four' => '4')
  );

  imprimirarreglo($arr);
?>


Resultado:

Roman:

one: I
two: II
three: III
four: IV

Arabic: one: 1
two: 2
three: 3
four: 4