php/sapi/cgi

Credits:
Ben Mansell, Stephen Landamore, Daniel Silverstone, Shane Caraveo

Running the FastCGI PHP module
------------------------------

There are two ways to run the resulting 'php' binary after the fastcgi
version has been built:

1) Configure your web server to run the PHP binary itself.

This is the simplest method, obviously you will have to configure your
web server appropriately. Some web servers may also not support this method,
or may not be as efficient.

2) Run PHP separately from the web server.

In this setup, PHP is started as a separate process entirely from the web
server. It will listen on a socket for new FastCGI requests, and deliver
PHP pages as appropriate. This is the recommended way of running PHP-FastCGI.
To run this way, you must start the PHP binary running by giving it a port
number to listen to on the command line, e.g.:

./php -b 8002

(you can also specify a bind address, e.g. ./php -b localhost:8002. However, this
 relies on the FastCGI devkit and does not seem to work properly)

You must also configure your web server to connect to the appropriate port
in order to talk to the PHP FastCGI process.

The advantage of running PHP in this way is that it entirely separates the
web server and PHP process, so that one cannot disrupt the other. It also
allows PHP to be on an entirely separate machine from the web server if need
be, you could even have several web servers utilising the same running PHP
process if required!


Using FastCGI PHP with Apache
=============================

First of all, you may well ask 'Why?'. After all, Apache already has mod_php.
However, there are advantages to running PHP with FastCGI. Separating the
PHP code from the web server removes 'bloat' from the main server, and should
improve the performance of non-PHP requests. Secondly, having one permanent
PHP process as opposed to one per apache process means that shared resources
like persistent database connections are used more efficiently.

First of all, make sure that the FastCGI module is enabled. You should have
a line in your config like:

    LoadModule fastcgi_module /usr/lib/apache/2.0/mod_fastcgi.so

Don't load mod_php, by the way. Make sure it is commented out!

    #LoadModule php4_module /usr/lib/apache/2.0/libphp4.so

Now, we'll create a fcgi-bin directory, just like you would do with normal
CGI scripts. You'll need to create a directory somewhere to store your
FastCGI binaries. We'll use /space/fcgi-bin/ for this example. Remember to
copy the FastCGI-PHP binary in there. (named just 'php')

    ScriptAlias /fcgi-bin/ /space/fcgi-bin/
    <Location /fcgi-bin/>
        Options ExecCGI
        SetHandler fastcgi-script
    </Location>

To have mod_fastcgi manage your php fastcgi processes for you, use the 
configuration directive FCGIServer (see mod_fastcgi docs for more
configuration information):

    FastCgiServer /fcgi-bin/php-cgi -processes 5

Next, we need to tell Apache to use the FastCGI binary /fcgi-bin/php to
deliver PHP pages. All that is needed is:

    AddType application/x-httpd-fastphp .php
    Action application/x-httpd-fastphp /fcgi-bin/php-cgi

Now, if you restart Apache, php pages should now be delivered!

Using FastCGI PHP with IIS or iPlanet
=====================================

FastCGI server plugins are available at www.caraveo.com/fastcgi/
Documentation on these are sparse.  iPlanet is not very tested,
and no makefile exists yet for unix based iPlanet servers.


Security
--------

Be sure to run the php binary as an appropriate userid. Also, firewall out
the port that PHP is listening on. In addition, you can set the environment
variable FCGI_WEB_SERVER_ADDRS to control who can connect to the FastCGI.
Set it to a comma separated list of IP addresses, e.g.:

export FCGI_WEB_SERVER_ADDRS=199.170.183.28,199.170.183.71


Tuning
------

There are a few tuning parameters that can be tweaked to control the
performance of FastCGI PHP. The following are environment variables that can
be set before running the PHP binary:

PHP_FCGI_CHILDREN  (default value: 8)

This controls how many child processes the PHP process spawns. When the
fastcgi starts, it creates a number of child processes which handle one
page request at a time. So by default, you will be able to handle 8
concurrent PHP page requests. Further requests will be queued.
Increasing this number will allow for better concurrency, especially if you
have pages that take a significant time to create, or supply a lot of data
(e.g. downloading huge files via PHP). On the other hand, having more
processes running will use more RAM, and letting too many PHP pages be
generated concurrently will mean that each request will be slow.

PHP_FCGI_MAX_REQUESTS (default value: 500)

This controls how many requests each child process will handle before
exitting. When one process exits, another will be created. This tuning is
necessary because several PHP functions are known to have memory leaks. If the
PHP processes were left around forever, they would be become very inefficient.