Install needed packages:
apt-get install libapache2-mod-fastcgi php5-fpm
Enable needed apache modules:
a2enmod actions alias fastcgi
Add fpm configuration for your site (/etc/php5/fpm/pool.d/site.name.conf)
[site.name] user = site_user group = site_group listen = /var/run/php5-fpm_site.name.sock listen.owner = www-data listen.group = www-data ;listen.mode = 0660 pm = dynamic pm.max_children = 5 pm.start_servers = 2 pm.min_spare_servers = 1 pm.max_spare_servers = 3 ;chroot = chdir = /
Add this to apache-site config:
<IfModule mod_fastcgi.c>
AddType application/x-httpd-fastphp5 .php
Action application/x-httpd-fastphp5 /php5-fcgi
Alias /php5-fcgi /usr/lib/cgi-bin/php5-fcgi_site.name
FastCgiExternalServer /usr/lib/cgi-bin/php5-fcgi_site.name -socket /var/run/php5-fpm_site.name.sock -pass-header Authorization
</IfModule>
Restart both fpm & apache2