These to funtions has excatly the same output, the only diff. is in which directory iterator they use. I hope someone out there can use it:
<?php
function listfilesin1 ($dir = ".", $depth=0) {
    echo "Dir: ".$dir."<br/>";
    foreach(new DirectoryIterator($dir) as $file) {
        if (!$file->isDot()) {
            if ($file->isDir()) {
                $newdir = $file->getPathname();
                listfilesin1($newdir, $depth+1);
            } else {
                echo "($depth)".$file->getPathname() . "<br/>";
            }
        }
    }
}
function listfilesin2 ($dir = ".", $depth=0) {
    echo "Dir: ".$dir."<br/>";
    foreach(new RecursiveDirectoryIterator($dir) as $file) {
        if ($file->hasChildren(false)) {
            $newdir = $file->key();
            listfilesin2($newdir, $depth+1);
        } else {
            echo "($depth)".$file->key() . "<br/>";
        }
    }
}
listfilesin();
?>

For some application I needed to reverse some standard iterators. 

So I mocked up this flexible function.
Enjoy

<?php
function reverse_iterator(Iterator $iterator){
    $type     = get_class($iterator);
    $array     = array_reverse(iterator_to_array($iterator), true);
    return new $type($array);
}
?>

<?php 
/*
How to store SPL Iterator results (rather than just echo-and-forget):

The library of Iterators  are object based, so you need to trick the little rascals into an array.  
Here's how (two ways) ...

1. Explicit typecasts: $a[] = (array)$Obj->objMethod();

2. Array definition: $a[] = array( key => $Obj->objMethod() );

Examples: DirectoryIterator()
*/

// 1. explicity typecast object as array
foreach ( new DirectoryIterator('./') as $Item )
{
  $fname = (array)$Item->getFilename();
  $dir_listing[] = $fname[0];
}

//
echo "<pre>";
print_r($dir_listing); unset($dir_listing);
echo"</pre><hr />";
//

// or

// 2. define array as key => object->method
foreach ( new DirectoryIterator('./') as $Item )
{
  $dir_listing[] = array (
    "fname" => $Item->getFilename(),        
    "path" => $Item->getPathname(),
    "size" => $Item->getSize(),                    
    "mtime" => $Item->getMTime() 
  );
}

//
echo "<pre>";
print_r($dir_listing); unset($dir_listing);
echo"</pre>";
//
?>

I have to correct my implementation from before. The example before only supported correct read-access but failed on setting new values after creation of the ArrayMultiObject. Also i had to correct a bug that occured from my CopyPasteChange into the comment textarea.

This snippet now hopefully implements a fully functional multidimensional array, represented by an ArrayObject:

<?php
class ArrayMultiObject extends ArrayObject
{
    function __construct($array, $flags = 0, $iterator_class = "ArrayIterator")
    {
        $objects = array();
        foreach($array AS $key => $value) {
            if(is_array($value)) {
                $objects[$key] = new ArrayMultiObject($value, $flags, $iterator_class);
            } else {
                $objects[$key] = $value;
            }
        }

        parent::__construct($objects, $flags, $iterator_class);
    }

    public function offsetSet($name, $value)
    {
        if(is_array($value)) {
            $value = new ArrayMultiObject($value);
        }

        return parent::offsetSet($name, $value);
    }
}
?>

There is a RecursiveFilterIterator that makes the above code much easier. And then ther is ParentIterator thta is already a filtering recursive iterator that only accepts elements that have children, with a RecursiveDirectoryIterator as inner iterator you would obviously get only the directories. Further more it ensures that it creates the correct children. All in all you simply need to do this:

$it = new RecursiveDirectoryIterator($path);
$it = new ParentIterator($it);
$it = new RecursiveIteratorIteator($it);

foreach($it as $dir  => $o) { ... }

Here's a sample implementation of the RecursiveDirectoryIterator class. It prints a simple treeview of a given directory:
<?php 
function recurse($it) { 
   echo '<ul>'; 
   for( ; $it->valid(); $it->next()) { 
       if($it->isDir() && !$it->isDot()) { 
           printf('<li class="dir">%s</li>', $it->current()); 
           if($it->hasChildren()) { 
               $bleh = $it->getChildren(); 
               echo '<ul>' . recurse($bleh) . '</ul>'; 
           } 
       } elseif($it->isFile()) { 
           echo '<li class="file">'. $it->current() . ' (' . $it->getSize(). ' Bytes)</li>'; 
       } 
   } 
   echo '</ul>'; 
} 

recurse(new RecursiveDirectoryIterator('D:/')); 
?>

Something to note that, at least to me, seems pretty important and is not entirely clear in the documentation is the fact that the ArrayObject class supports get/set on uni-dimensional keys and get ONLY on *passed* multi-dimensional keys/paths (see source below). If you, like me, need to support array accesss overloading for multi-dimensional data, you will need to derive from ArrayObject and overide the ArrayAccess interface methods to "walk" passed data and convert embedded arrays to objects of some kind... 

Reference Bug 34816 @ http://bugs.php.net/bug.php?id=34816.

Illustration of the issue:

$a = array(
    "test" => array(
        "one" => "dunno",
        "two" => array(
            "peekabo" => "do you see me?",
            "anyone" => array("there")
            )
        )
    );
$oArray = new ArrayObject($a);
var_dump($oArray);

$oArray["three"] = "No problems here.";

echo "\n\\test\\one == " . $oArray["test"]["one"] . "\n\n";

// NEITHER of the two below will work!
$oArray["test"]["one"] = "Yes I do!"; 
$oArray["test"]["yes"] = array(
    "hello" => "Goodbye!"
    );

var_dump($oArray);

---
Note from the extension author:
Actually there is RecursiveArrayObject and RecursiveArrayIterator to deal with recursive structures. However this does not always solve all multidimensional issues as expected.

This code is an example. By using classes like this, you gives a chance to create classes which extends another class but have most of the ability what a class extends ArrayObject (like multiple inheritance):

<?php

class foo 
{
    public $foo = 'foo';
} // class

class foobar extends foo implements ArrayAccess,IteratorAggregate,Countable
{
    public function offsetExists($offset)
    {
        $array = array(1, 2, 3, 4);
        return array_key_exists($offset, $array);
    }
    
    public function offsetGet($offset)
    {
        $array = array(1, 2, 3, 4);
        return $array[$offset];
    }
    
    public function offsetSet($offset, $value)
    {
        // Makes "array" to readonly
    }
    
    public function offsetUnset($offset)
    {
        // Makes "array" to readonly
    }
    
    function count()
    {
        $array = array(1, 2, 3, 4);
        return count($array);
    } // function
    
    function getArray()
    {
        return array(1, 2, 3, 4);
    } // function
    
    function getIterator()
    {
        return new ArrayIterator(array(1, 2, 3, 4));
    } // function
    
    function __toString()
    {
        return 'String test';
    } // function
} // class

$foobar = new foobar();
print $foobar[0].'<br/>';
print $foobar->foo.'<br/>';
print count($foobar).'<br/>';

foreach ($foobar as $k=>$v)
{
    print $k.'=>'.$v.'<br/>';
} // foreach

var_dump($foobar->getArray());

print $foobar;

/* Generated output:
1
foo
4
0=>1
1=>2
2=>3
3=>4
array
  0 => int 1
  1 => int 2
  2 => int 3
  3 => int 4
String test
*/
?>

For proper use you must be define all these methods except getArray()

Browse SPL's sources to be a very helpful think.

ps.: sry for my english