bnf/php-realpath-vs-opcache

Realpath symlink cache vs fpm opcache symlink entry point cache

This repository demonstrates that common assumptions about php realpath() are not (always) valid.

Background

The php realpath() function seems to use another cache than the php-fpm opcache path resolver. The tests in this repository therefore show that realpaths may be renewed while old scripts are still executed (that means: realpath($_SERVER['DOCUMENT_ROOT']) != __DIR__). See .travis/run-tests.sh for the detailed tests.

Possible workaround is to never use realpath(), but always rely on __DIR__/__FILENAME__. That's demonstrated in: https://github.com/bnf/static-docroot which is tested with TYPO3 7 LTS and TYPO3 8.6 to provide stable DOCUMENT_ROOT and SCRIPT_FILENAME values.

How to use

# on fedora
dnf install nginx coreutils php-fpm

# on debian/ubuntu
apt-get install nginx-extras realpath php-fpm

make check

make shutdown

Futher readings

https://codeascraft.com/2013/07/01/atomic-deploys-at-etsy/

zendtech/ZendOptimizerPlus#126 (comment)

zendtech/ZendOptimizerPlus#126 (comment)