<?php
require_once 'StringIterator.php';

class String implements IteratorAggregate {
  private $string;

  public function __construct($string = '') {
    $this->string = $string;
  }

  public function getIterator() {
    return new StringIterator($this->string);
  }

  // ...
}

$string = new String('Dies ist ein String.');

foreach ($string as $key => $value) {
  print $value . ' ';
}
?>