PHP tempdir helper function

tempdir.php

<?php

if (!function_exists('tempdir')) {
    /**
     * Create a unique temporary directory and return its path.
     *
     * Insipired by
     * @link https://stackoverflow.com/questions/1707801/making-a-temporary-dir-for-unpacking-a-zipfile-into
     * 
     * @param string $prefix
     * @param integer $mode
     * @param boolean $auto_delete
     * @return string
     */
    function tempdir($prefix = 'tmp', $mode = 0700, $auto_delete = true)
    {
        // abort if prefix contains unsafe characters
        if (strpbrk($prefix, '\\/:*?"<>|') !== false) {
            return false;
        }

        // create the directory
        do {
            $dirname = sys_get_temp_dir() . DIRECTORY_SEPARATOR . $prefix . Str::random(8);
        } while (!@mkdir($dirname, $mode));

        // clean up the filesystem when done
        if ($auto_delete) {
            // anonymous since we REALLY don't want to expose this functionality to general use
            $destroy_dir_func = function ($dirname) use (&$destroy_dir_func) {
                if (!is_dir($dirname)) {
                    return false;
                }
                $files = array_diff(scandir($dirname), ['.', '..']);
                foreach ($files as $file) {
                    if (is_dir($dirname . DIRECTORY_SEPARATOR . $file)) {
                        $destroy_dir_func($dirname . DIRECTORY_SEPARATOR . $file);
                    } else {
                        unlink($dirname . DIRECTORY_SEPARATOR . $file);
                    }
                }
                return rmdir($dirname);
            };

            register_shutdown_function($destroy_dir_func, $dirname);
        }

        return $dirname;
    }
}