(PHP 5 >= 5.4.0, PHP 7)
Examples:
Available callback arguments

The callback should accept up to three arguments: the current item, the current key and the iterator, respectively.

<?php

/**
 * Callback for RecursiveCallbackFilterIterator
 *
 * @param $current   Current item's value
 * @param $key       Current item's key
 * @param $iterator  Iterator being filtered
 * @return boolean   TRUE to accept the current item, FALSE otherwise
 */
function my_callback($current, $key, $iterator) {
    // Your filtering code here
}

?>

Recursive callback basic example

Filtering a recursive iterator generally involves two conditions. The first is that, to allow recursion, the callback function should return TRUE if the current iterator item has children. The second is the normal filter condition, such as a file size or extension check as in the example below.

<?php

$dir = new RecursiveDirectoryIterator(__DIR__);

// Filter large files ( > 100MB)
$files = new RecursiveCallbackFilterIterator($dir, function ($current, $key, $iterator) {
    // Allow recursion
    if ($iterator->hasChildren()) {
        return TRUE;
    }
    // Check for large file
    if ($current->isFile() && $current->getSize() > 104857600) {
        return TRUE;
    }
    return FALSE;
});
 
foreach (new RecursiveIteratorIterator($files) as $file) {
    echo $file->getPathname() . PHP_EOL;
}

?>

RecursiveCallbackFilterIterator::hasChildren

(PHP 5 >= 5.4.0, PHP 7) Check whether the inner iterator's current element has children

2016-02-24 16:20:03
RecursiveCallbackFilterIterator::__construct

(PHP 5 >= 5.4.0, PHP 7) Create a RecursiveCallbackFilterIterator from a RecursiveIterator

2016-02-24 16:20:02
RecursiveCallbackFilterIterator::getChildren

(PHP 5 >= 5.4.0, PHP 7) Return the inner iterator's children contained in a RecursiveCallbackFilterIterator

2016-02-24 16:20:02