Logrotate for php5-fpm ... first definition is for the log of the master-process, the second one is for every pool.

php5-fpm

/var/log/php5-fpm.log {
        daily
        rotate 21
        missingok
        notifempty
        sharedscripts
        postrotate
                kill -USR1 `cat /opt/php/logs/nginx.pid`
        endscript
}

/srv/http/*/log/php.error.log {
        daily
        copytruncate
        rotate 21
        missingok
        notifempty
}