[php] PHP-FPM doesn't write to error log

In your fpm.conf file you haven't set 2 variable which are only for error logging.

The variables are error_log (file path of your error log file) and log_level (error logging level).

; Error log file
; Note: the default prefix is /usr/local/php/var
; Default Value: log/php-fpm.log

error_log = log/php-fpm.log

; Log level
; Possible Values: alert, error, warning, notice, debug
; Default Value: notice

log_level = notice