Usage example:

<?php

$path = realpath('/etc');

$objects = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($path), RecursiveIteratorIterator::SELF_FIRST);
foreach($objects as $name => $object){
    echo "$name\n";
}

?>

This prints a list of all files and directories under $path (including $path ifself). If you want to omit directories, remove the RecursiveIteratorIterator::SELF_FIRST part.