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

No se nombra ningún archivo fuente ni ninguna prueba. Empieza reproduciendo el ejemplo de PHP contra /proc/1/fd/1 y leyendo el bug enlazado sobre la desreferenciación de pseudoenlaces; después, sigue la ruta de apertura de archivos para los descriptores de procfs. Se considera terminado cuando descriptores como /proc/1/fd/1 puedan abrirse y produzcan el resultado esperado en todas las SAPIs.