I am trying to install php with fpm on macports. I read somewhere that fpm means FastCGI process manager. Does that mean fastcgi and fpm are same? If they are same, then why
What Anthony says is absolutely correct, but I'd like to add that your experience will likely show a lot better performance and efficiency (due not to fpm-vs-fcgi but more to the implementation of your httpd).
For example, I had a quad-core machine running lighttpd + fcgi humming along nicely. I upgraded to a 16-core machine to cope with growth, and two things exploded: RAM usage, and segfaults. I found myself restarting lighttpd every 30 minutes to keep the website up.
I switched to php-fpm and nginx, and RAM usage dropped from >20GB to 2GB. Segfaults disappeared as well. After doing some research, I learned that lighttpd and fcgi don't get along well on multi-core machines under load, and also have memory leak issues in certain instances.
Is this due to php-fpm being better than fcgi? Not entirely, but how you hook into php-fpm seems to be a whole heckuva lot more efficient than how you serve via fcgi.