When using Apache and PHP, the common usage is to use mod_php which effectively loads php into memory for every single Apache instance. This limits a lot of features as well because of both PHP's limits, and how mod_php works.

By using an alternative approach, loading PHP through FastCGI, you get the ability to run Apache's worker MPM, which is a multi-threaded engine of Apache allowing it to use multi-CPU/multi-core systems more effectively than the older preforking method normally used. It also speeds up PHP scripts by still preloading the PHP interpretter in a different way.

We will explain further why this approach is beneficial.

Intended Audience

This article explains how to run PHP as a process which runs independently from Apache. It is written for server administrators who want to use a flexible and at the same time easy to manage PHP environment. The usefulness of this approach allows you to use the faster multi-threaded Apache MPM while using non-threadsafe PHP scripts.

What is mod_fcgid

mod_fcgid is an Apache module. It allows execution of external programs who create web documents as their output. This procedure is well-known from CGI (Common Gateway Interface) which is often used in shared hosting environments, for example to run Perl scripts.

mod_fcgid was created as a binary compatible alternative to mod_fastcgi. Both extend the traditional CGI principle with the feature that they use persistent processes, managed by a server component. This means that the web server will not launch a new process for every request as it is the case with CGI. The speed gain is enormous.

Using PHP with mod_fcgid offers a full-featured PHP environment combined with all the features that mod_fcgid provides. This solution has a lot of advantages over the traditional way of running PHP on a web server, while the only disadvantage seems to be that it is a little bit more difficult to be set up.

Advantages of mod_fcgid

Speed
- mod_fcgid seems to be as fast as the traditional mod_php Apache module. However, it also allows to be run on a multi threaded Apache server. For various reasons this still does not work reliable with mod_php4 / mod_php5.
Configuration flexibility
- With mod_fcgid it is possible to run many different PHP versions on the same server, and even with multiple different users.

Disadvantages of mod_fcgid

More complex installation process
- Installation of PHP using mod_fcgid is probably more difficult than setting up mod_php5, mainly because there is only a few documentation about it that can be found. However, since you found this document, you may be lucky…
Redirects may fail.
- The way that PHP works under FastCGI and mod_fcgid may not be compatible with current implementations of forwarding and internal routing used by your or other web applications. This may cause problems in functionality or even break the entire application.

Installation

Prerequisites

This manual is designed for Debian Etch servers. It expects a server running Apache 2.x. Basically this should work equally for other systems – they probably just use different paths and package names…

Installation of Packages

The following packages are required:

php5-cgi
- This is the CGI binary of PHP5. It was compiled with FCGI support and works perfectly together with mod_fcgid.
libapache2-mod-fcgid
- This is the FCGID module
apache2-mpm-worker
- This is the multi threaded multi-processing module (MPM) for Apache2. It replaces apache2-mpm-prefork with is a single-threaded MPM and is required by mod_php4 / mod_php5. Of course these packages must also be removed. Keep in mind that you may want to make a backup of your current php.ini, because php5-cgi will set up a new configuration file.

apt-get -u install php5-cgi libapache2-mod-fcgid apache2-mpm-worker

Configuration

Remove mod_php4 / mod_php5 if not already done

a2dismod php4
a2dismod php5

Enable mod_actions and mod_fcgid

a2enmod actions
a2enmod fcgid

Raise the communication timeout (= maximum execution time) for FCGI applications in /etc/apache2/mods-enabled/fcgid.conf by adding the “IPCCommTimeout” directive:

<IfModule mod_fcgid.c>
  AddHandler fcgid-script .fcgi
  SocketPath /var/lib/apache2/fcgid/sock

  # Communication timeout: Default value is 20 seconds
  IPCCommTimeout 60

  # Connection timeout: Default value is 3 seconds
  #IPCConnectTimeout 3
</IfModule>

Create a new file /etc/apache2/conf.d/php-fcgid.conf:

<IfModule !mod_php4.c>
  <IfModule !mod_php4_filter.c>
    <IfModule !mod_php5.c>
      <IfModule !mod_php5_filter.c>
        <IfModule !mod_php5_hooks.c>
          <IfModule mod_actions.c>
            <IfModule mod_alias.c>
              <IfModule mod_mime.c>
                <IfModule mod_fcgid.c>
                  # Path to php.ini - defaults to /etc/phpX/cgi
                  DefaultInitEnv PHPRC=/etc/php5/cgi

                  # Number of PHP childs that will be launched. Leave undefined to let PHP decide.
                  #DefaultInitEnv PHP_FCGI_CHILDREN 3

                  # Maximum requests before a process is stopped and a new one is launched
                  #DefaultInitEnv PHP_FCGI_MAX_REQUESTS 5000

                  # Define a new handler "php-fcgi" for ".php" files, plus the action that must follow
                  AddHandler php-fcgi .php
                  Action php-fcgi /fcgi-bin/php-fcgi-wrapper

                  # Define the MIME-Type for ".php" files
                  AddType application/x-httpd-php .php

                  # Define alias "/fcgi-bin/". The action above is using this value, which means that
                  # you could run another "php5-cgi" command by just changing this alias
                  Alias /fcgi-bin/ /var/www/fcgi-bin.d/php5-default/

                  # Turn on the fcgid-script handler for all files within the alias "/fcgi-bin/"
                  <Location /fcgi-bin/>
                    SetHandler fcgid-script
                    Options +ExecCGI
                  </Location>
                </IfModule>
              </IfModule>
            </IfModule>
          </IfModule>
        </IfModule>
      </IfModule>
    </IfModule>
  </IfModule>
</IfModule>

Next, create the directory which is chosen by the alias, and put in a symlink to the php5-cgi binary

mkdir /var/www/fcgi-bin.d/php5-default
ln -s /usr/bin/php5-cgi /var/www/fcgi-bin.d/php5-default/php-fcgi-wrapper

Finally, restart Apache:

/etc/init.d/apache2 restart

Additional configuration

It is also possible to run different versions of PHP, even with different users.

Enable mod_suexec:

a2enmod suexec

Create a new user:

adduser $username

For every instance of PHP, create a new subdirectory in /var/www/fcgi-bin.d:

mkdir /var/www/fcgi-bin.d/php$version-$username/

Instead of creating a symlink, this time you need to add a new file “php-fcgi-wrapper” inside this directory:

#!/bin/sh
# Wrapper for PHP-fcgi
# This wrapper can be used to define settings before launching the PHP-fcgi binary.

# Define the path to php.ini. This defaults to /etc/phpX/cgi.
#export PHPRC=/var/www/fcgi-bin.d/php5-web01/phprc
#export PHPRC=/etc/php5/cgi

# Define the number of PHP childs that will be launched. Leave undefined to let PHP decide.
#export PHP_FCGI_CHILDREN=3

# Maximum requests before a process is stopped and a new one is launched
#export PHP_FCGI_MAX_REQUESTS=5000

# Launch the PHP CGI binary
# This can be any other version of PHP which is compiled with FCGI support.
exec /usr/bin/php5-cgi

Make this script executable and change the user appropriately

# chmod a+x /var/www/fcgi-bin.d/php&amp;lt;version&amp;gt;-&amp;lt;username&amp;gt;/php-fcgi-wrapper
# chown <user>:<group> /var/www/fcgi-bin.d/php<version>-<username>/php-fcgi-wrapper

Modify the Apache configuration, e.g. in /etc/apache2/sites-enabled/web01:

<VirtualHost *:80>
  Servername web01.myserver.com
  DocumentRoot /var/www/websites/web01/
  SuexecUserGroup <user> <group>
  Action php-fcgi /fcgi-bin/php-fcgi-wrapper
  Alias /fcgi-bin/ /var/www/fcgi-bin.d/php<version>-<username>/
</VirtualHost>

Notice: It is important that user and group are owned by the same user and group as defined for the wrapper script above.

Restart Apache:

/etc/init.d/apache2 restart

Appendix

FAQ

How fast is it? Compared to mod_php5 the speed seems to be almost equal, probably just a little bit slower.
Can I turn off the PHP parser for a specific directory? Of course! You can simply disable the parser for directories. This is very useful for example to use WebDAV for editing PHP files. Using mod_php5 these files would be sent as plain HTML output:

<Location /dav/>
  RemoveHandler .php
</Location>

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