RecursiveCallbackFilterIterator::hasChildren

<?php

$dir = new RecursiveDirectoryIterator(__DIR__);

// Recursively iterate over XML files
$files = new RecursiveCallbackFilterIterator($dir, function ($current, $key, $iterator) {
    // Allow recursion into directories
    if ($iterator->hasChildren()) {
        return TRUE;
    }
    // Check for XML file
    if (!strcasecmp($current->getExtension(), 'xml')) {
        return TRUE;
    }
    return FALSE;
});

?>