ทำยังไงจึงจะใช้ SplHeap, ArrayIterator ในการเรียงลำดับไฟล์ที่เรียกมาด้วย RecursiveDIrectoryIterator+RecursiveIteratorIterator แล้วสามารถเรียกใช้ getDepth() ได้

<?php
/**
 * Create example folders and files (empty file).
 */


/**
 * Recursively delete directory and contents.
 *
 * @link https://stackoverflow.com/a/3338133/128761 Original source code.
 * @param string $dir
 * @return void
 */
function rrmdir($dir)
{
    if (is_dir($dir)) {
        $objects = scandir($dir);
        foreach ($objects as $object) {
            if ($object != "." && $object != "..") {
                if (is_dir($dir . DIRECTORY_SEPARATOR . $object) && !is_link($dir . "/" . $object))
                    rrmdir($dir . DIRECTORY_SEPARATOR . $object);
                else
                    unlink($dir . DIRECTORY_SEPARATOR . $object);
            }
        }
        rmdir($dir);
    }
}


if (is_dir('example-dir')) {
    rrmdir('example-dir');
}

if (!is_dir('example-dir')) {
    mkdir('example-dir/level1-1/1.1/1.1.1', 0777, true);
    mkdir('example-dir/level1-1/1.1/1.1.2', 0777, true);
    mkdir('example-dir/level1-1/1.1/1.1.3', 0777, true);
    mkdir('example-dir/level1-1/1.1/1.1.4', 0777, true);
    mkdir('example-dir/level1-1/1.2', 0777, true);
    mkdir('example-dir/level1-1/1.3', 0777, true);
    mkdir('example-dir/level1-2/2.1', 0777, true);
    mkdir('example-dir/level1-2/2.2', 0777, true);
    mkdir('example-dir/level1-3', 0777, true);
    mkdir('example-dir/level1-4', 0777, true);

    for ($i = 1; $i <= 2; $i++) {
        file_put_contents('example-dir/file' . $i . '.txt', '');
    }
    for ($i = 1; $i <= 5; $i++) {
        file_put_contents('example-dir/level1-1/file1.' . $i . '.txt', '');
    }
    for ($i = 1; $i <= 5; $i++) {
        file_put_contents('example-dir/level1-1/1.1/file1.1.' . $i . '.txt', '');
    }
    for ($i = 1; $i <= 5; $i++) {
        file_put_contents('example-dir/level1-2/file2.' . $i . '.txt', '');
    }
}

<?php

$targetDir = 'example-dir';


if (!is_dir($targetDir)) {
    die('Please run create-example-files.php');
} else {
    $targetDir = realpath($targetDir);
}

<?php


class BuildNestedArray
{


    protected function buildArrayDir($RII): array
    {
        $output = [];

        foreach ($RII as $File) {
            if (!$File->isDIr()) {
                continue;
            }

            if ($File->isDir()) {
                $subItem = [
                    'dir_' . $File->getFilename() => [
                        'filePath' => $File->getPathname(),// full path to file.
                        'depth' => $RII->getDepth(),
                        'children' => [],
                    ],
                ];
            }// endif; is dir.
            for ($depth = ($RII->getDepth() - 1); $depth >= 0; $depth--) {
                $subItem = [
                    'dir_' . $RII->getSubIterator($depth)->current()->getFilename() => [
                        'children' => $subItem,
                    ],
                ];
            }

            $output = array_merge_recursive($output, $subItem);

            unset($depth, $subItem);
        }// endforeach;
        unset($File);

        return $output;
    }// buildArrayDir


    public function build($RII): array
    {
        $output = [];
        $output = $this->buildArrayDir($RII);

        $i = 0;
        foreach ($RII as $filename => $File) {
            if ($File->isDIr()) {
                continue;
            }

            if (!$File->isDir()) {
                $subItem = [
                    'file_' . $i => [
                        'filePath' => $File->getPathname(),// full path to file.
                        'depth' => $RII->getDepth(),
                    ],
                ];
            }// endif not is dir.
            for ($depth = ($RII->getDepth() - 1); $depth >= 0; $depth--) {
                $subItem = [
                    'dir_' . $RII->getSubIterator($depth)->current()->getFilename() => [
                        'children' => $subItem,
                    ],
                ];
            }// endfor;
            $output = array_merge_recursive($output, $subItem);

            unset($depth, $subItem);

            $i++;
        }// endforeach;
        unset($File, $filename, $i);

        return $output;
    }// build


}

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <[email protected]>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Finder\Iterator;

/**
 * SortableIterator applies a sort on a given Iterator.
 *
 * @author Fabien Potencier <[email protected]>
 */
class SortableIterator implements \IteratorAggregate
{
    public const SORT_BY_NONE = 0;
    public const SORT_BY_NAME = 1;
    public const SORT_BY_TYPE = 2;
    public const SORT_BY_ACCESSED_TIME = 3;
    public const SORT_BY_CHANGED_TIME = 4;
    public const SORT_BY_MODIFIED_TIME = 5;
    public const SORT_BY_NAME_NATURAL = 6;

    private $iterator;
    private $sort;

    /**
     * @param \Traversable $iterator The Iterator to filter
     * @param int|callable $sort     The sort type (SORT_BY_NAME, SORT_BY_TYPE, or a PHP callback)
     *
     * @throws \InvalidArgumentException
     */
    public function __construct(\Traversable $iterator, $sort, bool $reverseOrder = false)
    {
        $this->iterator = $iterator;
        $order = $reverseOrder ? -1 : 1;

        if (self::SORT_BY_NAME === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                return $order * strcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
            };
        } elseif (self::SORT_BY_NAME_NATURAL === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                return $order * strnatcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
            };
        } elseif (self::SORT_BY_TYPE === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                if ($a->isDir() && $b->isFile()) {
                    return -$order;
                } elseif ($a->isFile() && $b->isDir()) {
                    return $order;
                }

                return $order * strcmp($a->getRealPath() ?: $a->getPathname(), $b->getRealPath() ?: $b->getPathname());
            };
        } elseif (self::SORT_BY_ACCESSED_TIME === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                return $order * ($a->getATime() - $b->getATime());
            };
        } elseif (self::SORT_BY_CHANGED_TIME === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                return $order * ($a->getCTime() - $b->getCTime());
            };
        } elseif (self::SORT_BY_MODIFIED_TIME === $sort) {
            $this->sort = static function (\SplFileInfo $a, \SplFileInfo $b) use ($order) {
                return $order * ($a->getMTime() - $b->getMTime());
            };
        } elseif (self::SORT_BY_NONE === $sort) {
            $this->sort = $order;
        } elseif (\is_callable($sort)) {
            $this->sort = $reverseOrder ? static function (\SplFileInfo $a, \SplFileInfo $b) use ($sort) { return -$sort($a, $b); } : $sort;
        } else {
            throw new \InvalidArgumentException('The SortableIterator takes a PHP callable or a valid built-in sort algorithm as an argument.');
        }
    }


    /**
     * @return \Traversable
     */
    public function getIterator()
    {
        if (1 === $this->sort) {
            return $this->iterator;
        }

        $array = iterator_to_array($this->iterator, true);

        if (-1 === $this->sort) {
            $array = array_reverse($array);
        } else {
            uasort($array, $this->sort);
        }

        return new \ArrayIterator($array);
    }


}

<?php

require '_config.php';
require '_BuildNestedArray.php';


// $targetDir = 'example-dir';


$RDI = new \RecursiveDirectoryIterator(
    $targetDir,
    \FilesystemIterator::SKIP_DOTS
);


$RII = new \RecursiveIteratorIterator(
    $RDI,
    \RecursiveIteratorIterator::SELF_FIRST,
    \RecursiveIteratorIterator::CATCH_GET_CHILD
);


$totalFiles = iterator_count($RII);
echo 'Total files: ' . $totalFiles . '<br>' . PHP_EOL;


// display files and folders listing --------------------------
echo '<ol>' . PHP_EOL;
foreach ($RII as $File) {
    echo '<li>' . PHP_EOL;
    echo $File->getPathname();
    echo '</li>' . PHP_EOL;
}// endforeach;
echo '</ol>' . PHP_EOL;
// end display files and folders listing -----------------------


// build nested array ----------------------------------------
$BuildNestedArray = new BuildNestedArray();
$nestedArray = $BuildNestedArray->build($RII);
echo '<hr>' . PHP_EOL;
echo '<h5>Nested array</h5>' . PHP_EOL;
echo '<pre>' . print_r($nestedArray, true) . '</pre>';
unset($nestedArray, $BuildNestedArray);
// end build nested array ------------------------------------

<?php

require '_config.php';
require '_BuildNestedArray.php';


// $targetDir = 'example-dir';


$RDI = new \RecursiveDirectoryIterator(
    $targetDir,
    \FilesystemIterator::SKIP_DOTS
);


$RII = new \RecursiveIteratorIterator(
    $RDI,
    \RecursiveIteratorIterator::SELF_FIRST,
    \RecursiveIteratorIterator::CATCH_GET_CHILD
);


$totalFiles = iterator_count($RII);
echo 'Total files: ' . $totalFiles . '<br>' . PHP_EOL;


// paginated files listing. ------------------------------
// prepare data for limit pagination
$offset = ($_GET['offset'] ?? 0);
if (!is_numeric($offset)) {
    $offset = 0;
} else {
    $offset = (int) $offset;
}
$limit = 12;
$paginated = true;
// limit pagination here.
$RII = new \LimitIterator($RII, $offset, $limit);
// end paginated files listing. --------------------------


// display files and folders listing --------------------------
echo '<ol>' . PHP_EOL;
foreach ($RII as $File) {
    echo '<li>' . PHP_EOL;
    echo $File->getPathname();
    echo '</li>' . PHP_EOL;
}// endforeach;
echo '</ol>' . PHP_EOL;
// end display files and folders listing -----------------------


// display pagination -----------------------------------------
if (isset($paginated) && true === $paginated && $totalFiles > $limit) {
    echo '<br>' . PHP_EOL;
    $totalPages = ceil($totalFiles/$limit);
    for ($i = 1; $i <= $totalPages; $i++) {
        $loopOffset = (int) (($i-1)*$limit);
        if ($loopOffset === $offset) {
            echo '<strong>';
        }
        echo '<a href="?offset=' . $loopOffset . '">' . $i . '</a> ';
        if ($loopOffset === $offset) {
            echo '</strong>';
        }
    }
    unset($i, $totalPages, $loopOffset);
}
// end display pagination --------------------------------------


// build nested array ----------------------------------------
$BuildNestedArray = new BuildNestedArray();
$nestedArray = $BuildNestedArray->build($RII);
echo '<hr>' . PHP_EOL;
echo '<h5>Nested array</h5>' . PHP_EOL;
echo '<pre>' . print_r($nestedArray, true) . '</pre>';
unset($nestedArray, $BuildNestedArray);
// end build nested array ------------------------------------

<?php

require '_config.php';
require '_BuildNestedArray.php';
require '_SymfonySort.php';


// $targetDir = 'example-dir';


$RDI = new \RecursiveDirectoryIterator(
    $targetDir,
    \FilesystemIterator::SKIP_DOTS
);


$RII = new \RecursiveIteratorIterator(
    $RDI,
    \RecursiveIteratorIterator::SELF_FIRST,
    \RecursiveIteratorIterator::CATCH_GET_CHILD
);


$totalFiles = iterator_count($RII);
echo 'Total files: ' . $totalFiles . '<br>' . PHP_EOL;


// sort the list ----------------------------------------
$RII = (new \Symfony\Component\Finder\Iterator\SortableIterator($RII, 6))->getIterator();
// end sort the list ------------------------------------


// paginated files listing. ------------------------------
// prepare data for limit pagination
$offset = ($_GET['offset'] ?? 0);
if (!is_numeric($offset)) {
    $offset = 0;
} else {
    $offset = (int) $offset;
}
$limit = 12;
$paginated = true;
// limit pagination here.
$RII = new \LimitIterator($RII, $offset, $limit);
// end paginated files listing. --------------------------


// display files and folders listing --------------------------
echo '<ol>' . PHP_EOL;
foreach ($RII as $File) {
    echo '<li>' . PHP_EOL;
    echo $File->getPathname();
    echo '</li>' . PHP_EOL;
}// endforeach;
echo '</ol>' . PHP_EOL;
// end display files and folders listing -----------------------


// display pagination -----------------------------------------
if (isset($paginated) && true === $paginated && $totalFiles > $limit) {
    echo '<br>' . PHP_EOL;
    $totalPages = ceil($totalFiles/$limit);
    for ($i = 1; $i <= $totalPages; $i++) {
        $loopOffset = (int) (($i-1)*$limit);
        if ($loopOffset === $offset) {
            echo '<strong>';
        }
        echo '<a href="?offset=' . $loopOffset . '">' . $i . '</a> ';
        if ($loopOffset === $offset) {
            echo '</strong>';
        }
    }
    unset($i, $totalPages, $loopOffset);
}
// end display pagination --------------------------------------


// build nested array ----------------------------------------
$BuildNestedArray = new BuildNestedArray();
$nestedArray = $BuildNestedArray->build($RII);
echo '<hr>' . PHP_EOL;
echo '<h5>Nested array</h5>' . PHP_EOL;
echo '<pre>' . print_r($nestedArray, true) . '</pre>';
unset($nestedArray, $BuildNestedArray);
// end build nested array ------------------------------------