title: Difference between DirectoryIterator and FileSystemIterator
body: <p>PHP 5 introduced <a href="http://us.php.net/manual/en/class.directoryiterator.php">DirectoryIterator</a>, and PHP 5.3 introduced <a href="http://us.php.net/manual/en/class.filesystemiterator.php">FileSystemIterator</a>.</p>
  
  <p><code>FileSystemIterator</code> extends <code>DirectoryIterator</code>, but the documentation fails to say what extra features it brings.</p>
  
  <p>Can you tell the difference between <code>DirectoryIterator</code> and <code>FileSystemIterator</code>?</p>