gistfile1.php

<?php
$array = array(
    0 => 0,
    1 => 1,
    2 => 2,
    3 => array(
      0 => 30,
      1 => 31,
      2 => 32,
      3 => 33,
      4 => 34,
    ),
    4 => 4,
    5 => 5,
);

$obj = new ArrayObject($array);

function updateArray($obj) {
    $iterator = $obj->getIterator();
    
    while($iterator->valid()) {
    
      if (is_array($iterator->current())) {
        $obj->offsetSet(
          $iterator->key(), 
          new ArrayObject($iterator->current()))
        ;
        updateArray($obj->offsetGet($iterator->key()));
      } else {
        $obj->offsetSet(
          $iterator->key(),
          $obj->offsetGet($iterator->key()) + 100)
        ;
      }
      
      $iterator->next();
    }
}

updateArray($obj);

var_dump($obj);
/*
Output
object(ArrayObject)[1]
  int 100
  int 101
  int 102
  
    object(ArrayObject)[3]
      int 130
      int 131
      int 132
      int 133
      int 134
  int 104
  int 105
*/