Apache2 mpm worker + fastcgi + php5-fpm on debian

Install required packages:

# apt-get install libapache2-mod-fastcgi apache2-mpm-worker php5-fpm

To install php5-fpm on debian squeeze you can add dotdeb repository to your sources.list

deb http://packages.dotdeb.org stable all
deb-src http://packages.dotdeb.org stable all

Then run:

# wget -O- "http://www.dotdeb.org/dotdeb.gpg" | apt-key add -
# apt-get update

Configure php5-fpm pool in /etc/php5/fpm/pool.d/, www.conf by default, but you can change the name and set a new one based on virtual host.

user = user
group = group
listen = /var/run/php5-fpm.sock
listen.owner = user
listen.group = group
pm = dynamic
pm.max_children = 150
pm.start_servers = 30
pm.min_spare_servers = 15
pm.max_spare_servers = 40
pm.max_requests = 1000

You can also set a sock file name identifying the pool name. I am using only one pool in the server, so I leave it as default.
Configure Apc in /etc/php5/fpm/conf.d/20-apc

extension=apc.so
apc.enabled=1
apc.stat=0
apc.mmap_file_mask = /tmp/apc-XXXXXX
apc.enable_cli = 0
apc.max_file_size = 2M
apc.stat_ctime = 0
apc.shm_size = 128M
apc.canonicalize=0

Restart php5-fpm with the new configuration:

/etc/init.d/php5-fpm restart

Now, configure apache to be able to pass php requests to php5-fpm server:

Enable actions module if it isn’t enabled yet

# a2enmod actions

Configure fastcgi, edit file /etc/apache2/mods-enabled/fastcgi.conf

<IfModule mod_fastcgi.c>
  AddHandler fastcgi-script .fcgi
  #FastCgiWrapper /usr/lib/apache2/suexec
  FastCgiIpcDir /var/lib/apache2/fastcgi

  Alias /php5.fcgi /var/lib/apache2/fastcgi/php5.fcgi
  FastCGIExternalServer /var/lib/apache2/fastcgi/php5.fcgi -flush -socket /var/run/php5-fpm.sock
  # application/x-httpd-php                        phtml pht php
  # application/x-httpd-php3                       php3
  # application/x-httpd-php4                       php4
  # application/x-httpd-php5                       php
  <FilesMatch ".+\.ph(p[345]?|t|tml)$">
    SetHandler application/x-httpd-php
  </FilesMatch>
  Action application/x-httpd-php /php5.fcgi
  <Directory "/var/lib/apache2/fastcgi">
    Order deny,allow
    Deny from all
    <Files "php5.fcgi">
      Order allow,deny
      Allow from all
    </Files>
  </Directory>

</IfModule>

If you have several virtualhosts, each one with diferents pools, you can especifly the FastCGIExternalServer directive in each virtualhost configuration.

Create file /var/lib/apache2/fastcgi/php5.fcgi

# touch /var/lib/apache2/fastcgi/php5.fcgi

Restart apache:

# apachectl restart

And now test if your php files are served correctly by apache.