File descriptors / some procfs entries not openable by php

Description

The following code:

<?php
file_put_contents("/proc/1/fd/1", "hi");

Resulted in this output:

file_put_contents(/proc/1/fd/1): failed to open stream: No such file or directory

But I expected this output instead:

2

This is highly impactful for containerized PHP environments. php-fpm has unique workarounds that they've utilized, and in the past the fd stream wrapper was implemented to support managing the current process's file descriptors, but if you are in a different SAPI and/or utilize forking or execing to other PHP scripts, stdout in a docker container quickly turns into a black hole in terms of container logging, where it's expected that all logs are sent to the PID 1 stdout/err. See: https://bugs.php.net/bug.php?id=53465 where they hypothesize this is due to PHP incorrectly attempts to dereference the pseudo-symlink before opening it. The hypothesis makes sense to me. It'd be nice to see this fixed for all file descriptors.

PHP Version

7.4

Operating System

Centos 7.9

ソースファイルもテストも指定されていません。まず /proc/1/fd/1 に対して PHP の例を再現し、擬似シンボリックリンクのデリファレンスに関するリンク先の bug を読んでから、procfs ディスクリプタのファイルオープン経路を追跡してください。/proc/1/fd/1 のようなディスクリプタを開くことができ、すべての SAPIs で期待される結果が得られれば完了です。