Description:
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We use NGINX with FPM backend configured to write to syslog using custom facility: 

/etc/php-fpm.conf
-----------------
include=/etc/php-fpm.d/*.conf
[global]
error_log = syslog
syslog.facility = local3
syslog.ident = php-fpm
log_level = notice
emergency_restart_threshold = 0
emergency_restart_interval = 0
process_control_timeout = 0
daemonize = yes

/etc/php-fpm.d/www.conf
-----------------------
[www]
listen = /run/php-fpm-www.sock
listen.backlog = 1024
listen.allowed_clients = 
listen.owner = nginx
listen.group = nginx
listen.mode = 0660
user = phpwww
group = phpwww
pm = static
pm.max_children = 8
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 35
pm.max_requests = 512
catch_workers_output = yes


Until latest release of PHP 7.2 (and lower), this configuration was working fine and logs were correctly written to syslog as expected, but after upgrading to PHP 7.3.x or even 7.4.x, this doesn't work anymore. The only entries forwarded to syslog are those related to FPM startup and any other error (eg. syntax errors) is not being catched.

If we switch php-fpm logging to file then logs are correctly written to that file, so the issue exists only with syslog.


Test script:
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<?php
error_log('some error');

Expected result:
----------------
New syslog entry is created:
Mar  3 12:00:42 web php-fpm[xxx]: [WARNING] [pool www] child xxx said into stderr: "NOTICE: PHP message: some error"

Actual result:
--------------
No syslog entry is created