If you are using PHP-FPM with Apache and you would like to separate the error logging by user, directory or virtual host, you can use the ProxyFCGISetEnvIf directive

In a server level Apache .conf file

<Directory /home/user/public_html>
ProxyFCGISetEnvIf "true" PHP_ADMIN_VALUE "error_log=/var/log/php-fpm/user/error.log"
</Directory>

In this case, the error log for user would be

/var/log/php-fpm/user/error.log


Set up the ACL (AMI 2 Linux)

setfacl -m u:user:x /var/log/php-fpm
setfacl -m u:user:rx /var/log/php-fpm/user
setfacl -d -m u:user:r /var/log/php-fpm/user

Test it with

sudo su user
more /var/log/php-fpm/user/error.log

Credit to:

Comment from PHP.net (documentation)

https://www.php.net/manual/en/install.fpm.configuration.php#123335