php_8/iterators/recursion_dir.php

<?php
function recursion_dir($path)
{
    static $depth = 0;

    $dir = opendir($path);
    while (($file = readdir($dir)) !== false) {
        if ($file == '.' || $file == '..' ) continue;
        echo str_repeat('-', $depth)." $file<br />";

        if (is_dir("$path/$file")) {
            $depth++;
            recursion_dir("$path/$file");
            $depth--;
        }
    }
    closedir($dir);
}

recursion_dir('.');