PHP FastCGI

The PHP FastCGI Process Manager or PHP-FPM in short is server running in the background. When a web browser requests a web page which is made by a PHP script, the web server (Nginx in our case) will forward the request to the PHP-FPM server who will process it. PHP-FPM then sends the script output back to webserver. At last the webserver forwards the output back to the web browser.

Install PHP-FPM

$ sudo apt install php7-fpm

The Ubuntu upstart service php7-fpm is installed and started.

PHP Configuration

php.ini

Change the following in /etc/php/7.0/php.ini:

cgi.fix_pathinfo=0

php-fpm.conf

The global PHP-FPM configuration is stored in /etc/php5/fpm/php-fpm.conf. Nothing needs to be changed there.

Pools

Server pools are defined in the /etc/php5/fpm/pools.d directory. Only one pool is defined /etc/php5/fpm/pools.d/www.conf.

pm.status_path = /fpm_status

catch_workers_output = yes

PHP Scripts Server Restart

To apply the configuration changes, the server needs to be restarted:

$ sudo restart php5-fpm

Nginx Configuration

There are to parts to this.

PHP Backend Server

First we add a backend-server definition to the main Nginx HTTP server configuration. With this Nginx will be able to becomes a sort of proxy server and request content to be delivered to clients from the PHP-FPM server.

Create the php-backend.conf configuration file in the /etc/nginx/http-conf.d/ directory:

#
# PHP FastCGI Process Manager (FPM)
#
upstream php-backend {

    # Unix Socket to PHP 7 FPM server
    server unix:/run/php/php7.0-fpm.sock;
}

# Number and size of the buffers used for reading a response from the
# FastCGI server.
# Default: 8 8k (1 system memory page size)
fastcgi_buffers 128 8k; # 1 MB total

Like all other file in the /etc/nginx/http-conf.d directory, it will be automatically included in the main Nginx HTTP server configuration.

PHP Script Handler

Secondly we define under what circumstances, processing is turned over to the PHP-FPM server. As this can be defined at any level (http, server, location, etc), we create a file /etc/nginx/php-handler.conf to be included where appropriate.

#
# Pass PHP scripts to the cgi server
location ~ \.php$ {
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        include fastcgi_params;
        fastcgi_index index.php;
        fastcgi_pass php-backend;
}

FastCGI Parameters

The file /etc/nginx/fastcgi_params passes down important environment variables from the context of the request down to the scripts handling executable (e.g. PHP):

#
# FastCGI Settings
#

#
# httpoxy Mitigation - See https://httpoxy.org/
fastcgi_param  HTTP_PROXY           "";

#
# Pass Nginx variables to the CGI executeable environment
#

# Request
fastcgi_param  QUERY_STRING         $query_string;
fastcgi_param  REQUEST_METHOD       $request_method;
fastcgi_param  CONTENT_TYPE         $content_type;
fastcgi_param  CONTENT_LENGTH       $content_length;

# Script
fastcgi_param  SCRIPT_FILENAME      $document_root$fastcgi_script_name;
fastcgi_param  SCRIPT_NAME          $fastcgi_script_name;
fastcgi_param  PATH_INFO            $fastcgi_path_info;
fastcgi_param  PATH_TRANSLATED      $document_root$fastcgi_path_info;
fastcgi_param  REQUEST_URI          $request_uri;
fastcgi_param  DOCUMENT_URI         $document_uri;
fastcgi_param  DOCUMENT_ROOT        $document_root;
fastcgi_param  SERVER_PROTOCOL      $server_protocol;

# Proxy
fastcgi_param  GATEWAY_INTERFACE    CGI/1.1;
fastcgi_param  SERVER_SOFTWARE      nginx/$nginx_version;

# Network
fastcgi_param  REMOTE_ADDR          $remote_addr;
fastcgi_param  REMOTE_PORT          $remote_port;
fastcgi_param  SERVER_ADDR          $server_addr;
fastcgi_param  SERVER_PORT          $server_port;
fastcgi_param  SERVER_NAME          $server_name;

# Protocol
fastcgi_param  REQUEST_SCHEME       $scheme;
fastcgi_param  HTTPS                $https if_not_empty;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

To apply any changes made in to the Nginx configuration, the server needs to be restarted:

$ sudo service nginx restart

References