My configuration is like this:
Centos 6.3
Plesk 11.5
PHP 5.4.18
Apache 2.2.15
PHP API: 20100412
Server API: CGI/FastCGI
I use php as fastcgi. But I want to use APC or XCache. And it seems like FastCGI doesn't work well with opcache. So I read that it is better to use PHP-FPM. So how can I enable or install PHP-FPM ?
I read some tutorials and they offer to compile apache with fpm but it seems like a big risk for me. I'm not well-informed in servers.
I'm not sure whether I use mod_fastcgi or mod_fcgid. In my /etc/httpd/conf.d/ folder I have fcgid.conf file. So I think I use fcgid. Is it correct?
My Plesk has this setting: http://s11.postimg.org/pgqxwmmr7/fast.jpg
I'm curious if I install php-fpm can it brak my webserver or will any other problem occur ?
When dealing with Apache and FPM you should be using mod_fastcgi and not mod_fcgid.
I created this documentation a while ago and it seems to have helped quite a few people in the past, so perhaps it will also help you -> https://gist.github.com/diemuzi/3849349
As for breaking the web server... That's an iffy question. Since FPM is a standalone and does not need Apache to run, it possible that your current Apache setup might need some additional "tweaking" to make it work the right way again. Furthermore, since you are running Plesk and as it does not currently offer FPM support, there is also a good chance that you could possibly break your Plesk setup.
If you were not using some proprietary control panel software to manage your server and did things the old fashioned way by manually installing (or even using packages from your distro) then all of this would be a very simple solution for you.