RecursiveIterator with directories in PHP

I want to list directories and files in directories like:

Array(
    [0] => 2014
    [1] => images
    [2] => videos
)

All of the directories in this array are in the "web_public" directory of my website. But there are some other directories within it which I don't want to read. The complete web_public is:

2014
images
videos
css
js
... and so on

Here is what I'm doing but doesn't work:

$objects = array();
foreach($dirs_to_read as $dir) {
    $dir = 'web_public/'.$dir;
    $objects = array_merge($objects, new RecursiveDirectoryIterator($dir));                
}   
$objects = new RecursiveIteratorIterator($objects);

From PHP 5 you can use RecursiveDirectoryIterator to get file array. For example:

$path = __DIR__;

$directory = new \RecursiveDirectoryIterator(
    $path,
    RecursiveDirectoryIterator::SKIP_DOTS
    | RecursiveDirectoryIterator::CURRENT_AS_PATHNAME
    | RecursiveDirectoryIterator::KEY_AS_FILENAME
);

$iterator = new \RecursiveIteratorIterator($directory);
$array    = iterator_to_array($iterator);

print_r($array);

Outputs something like:

Array
(
    [demo.php] => /path/tp/demo.php
)