the fpm process supports the USER2 signal, which is used to reload the config file.
kill -USR2 [pid]
should do the trick.
FastCGI Process Manager (FPM)
Table of Contents
FPM (FastCGI Process Manager) is an alternative PHP FastCGI implementation with some additional features (mostly) useful for heavy-loaded sites.
These features include:
advanced process management with graceful stop/start;
ability to start workers with different uid/gid/chroot/environment, listening on different ports and using different php.ini (replaces safe_mode);
stdout and stderr logging;
emergency restart in case of accidental opcode cache destruction;
accelerated upload support;
"slowlog" - logging scripts (not just their names, but their PHP backtraces too, using ptrace and similar things to read remote process' execute_data) that are executed unusually slow;
fastcgi_finish_request() - special function to finish request and flush all data while continuing to do something time-consuming (video converting, stats processing etc.);
dynamic/static child spawning;
basic SAPI status info (similar to Apache mod_status);
php.ini-based config file.
Init script setup
You will probably want to create an init script for your new php-fpm. Fortunately, PHP 5.3.3 provides one for you, which you should copy to your init directory and change permissions:
$ cp <php-5.3.3-source-dir>/sapi/fpm/init.d.php-fpm.in /etc/init.d/php-fpm
$ chmod 755 /etc/init.d/php-fpm
It requires a certain amount of setup. First of all, make sure your php-fpm.conf file is set up to create a PID file when php-fpm starts. E.g.:
pid = /var/run/php-fpm.pid
(also make sure your php-fpm user has permission to create this file).
Now open up your new init script (/etc/init.d/php-fpm) and set the variables at the top to their relevant values. E.g.:
Your init script is now ready. You should now be able to start, stop and reload php-fpm:
$ /etc/init.d/php-fpm start
$ /etc/init.d/php-fpm stop
$ /etc/init.d/php-fpm reload
The one remaining thing you may wish to do is to add your new php-fpm init script to system start-up. E.g. in CentOS:
$ /sbin/chkconfig php-fpm on
Disclaimer: Although I did just do this on my own server about 20 mins ago, everything I've written here is off the top of my head, so it may not be 100% correct. Also, allow for differences in system setup. Some understanding of what you are doing is assumed.