here's the code for reproducing the bug.

<?php
/**
 * Created by RexMin.
 * Description.
 * Email: rexmin@futunn.com
 * Date: 2020/9/4
 * Time: 14:40
 */

class Test
{
    protected $path = 'directory';

    public function createTestFiles ()
    {
        $amount = 63;

        if (!is_dir($this->path)) {
            mkdir($this->path);
        }

        foreach (scandir($this->path) as $filename) {
            @unlink("{$this->path}/$filename");
        }

        for ($num = 1; $num <= $amount; $num++) {
            fopen("{$this->path}/{$num}.txt", "a");
        }
    }

    public function runTest()
    {
        echo 'get by foreach: ' . $this->getByForeach() . PHP_EOL;
        echo 'get by foreach with rewind: ' . $this->getByForeachWithRewind() . PHP_EOL;
        echo 'get by foreach after foreach: ' . $this->getByForeachAfterForeach() . PHP_EOL;
        echo 'get by loop: ' . $this->getByloop() . PHP_EOL;
        echo 'get by iterator_to_array: ' . $this->getByIteratorToArray() . PHP_EOL;
        echo 'get by iterator_to_array with rewind: ' . $this->getByIteratorToArrayWithRewind() . PHP_EOL;
    }

    public function getByForeach()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        $count = 0;
        foreach ($directory as $filename => $fileInfo) {
            $count++;
        }

        return $count;
    }

    public function getByForeachWithRewind()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        $count = 0;
        $directory->rewind();
        foreach ($directory as $filename => $fileInfo) {
            $count++;
        }

        return $count;
    }

    public function getByForeachAfterForeach()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        $count = 0;
        foreach ($directory as $filename => $fileInfo) {
            // do nothing
        }
        foreach ($directory as $filename => $fileInfo) {
            $count++;
        }

        return $count;
    }

    public function getByLoop()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        $count = 0;
        while ($directory->valid()) {
            $count++;
            $directory->next();
        }

        return $count;
    }

    public function getByIteratorToArray()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        return count(iterator_to_array($directory));
    }

    public function getByIteratorToArrayWithRewind()
    {
        $directory = new RecursiveDirectoryIterator($this->path);
        $directory->rewind();
        return count(iterator_to_array($directory));
    }
}

$test = new Test();
$test->createTestFiles();
$test->runTest();

I cannot reproduce the reported behavior.

> please use the patch file to reproduce the bug.

Not sure if you tried to add some file as patch, but that won't
necessarily work.  Please make such scripts publicly available
somewhere else (e.g. gist.github.com, pastebin.com), and share the
link here.

Somehow I cannot upload my test code by using patch file.So I paste the test code in the previos comment.please check.

For some reason I missed that script.  Anyhow, I cannot reproduce
the issue with that script.  All six methods return the expected
65.

Hi there, I finally find out that the reason to problem is actually the environment.

I was using the docker with the `WSL 2 based engine` under the Windows system. As soon as I changed the docker engine into `Legacy Hyper-V backend`, the problem disappeared.

Thanks!  Then this is unlikely to be a PHP issue.

For reference, a ticket on the core of this issue is filed at Microsoft's WSL2 Linux Kernel repository: https://github.com/microsoft/WSL2-Linux-Kernel/issues/187