PHP and PHP-FPM

PHP (PHP Hypertext Preprocessor) is a source scripting language specially designed for web application development. In 2024, PHP represented a little less than 80% of the web pages generated in the world. PHP is open source and is the core of the most famous CMS (WordPress, Drupal, Joomla!, Magento, and others).

PHP integrates PHP-FPM (FastCGI Process Manager) since version 5.3.3. The FastCGI version of PHP brings additional functionalities.

Generalities

CGI (Common Gateway Interface) and FastCGI allow communication between the web server (Apache, Nginx, and others) and a development language (PHP, Python, Java):

• In the case of CGI, each request creates a new process, which is less efficient in performance.
• FastCGI relies on a certain number of processes to treat its client requests.

PHP-FPM, in addition to better performances, brings:

• The possibility of better partitioning the applications: launching processes with different uid/gid, with personalized php.ini files,
• The management of the statistics,
• Log management,
• Dynamic management of processes and restart without service interruption ('graceful').

Note

Since Apache has a PHP module, php-fpm is more commonly used on an Nginx server.

Choose a PHP version

Rocky Linux 10, as with its upstream, no longer has modules. The version of PHP is what is available from the Appstream repository. To check the available version of PHP use:

dnf whatprovides php

Last metadata expiration check: 0:00:03 ago on Wed 22 Oct 2025 03:58:30 PM UTC.

php-8.3.19-1.el10_0.x86_64 : PHP scripting language for creating dynamic web sites
Repo        : @System
Matched from:
Provide    : php = 8.3.19-1.el10_0

php-8.3.19-1.el10_0.x86_64 : PHP scripting language for creating dynamic web sites
Repo        : appstream
Matched from:
Provide    : php = 8.3.19-1.el10_0

You can now proceed to the installation of the PHP engine.

PHP cgi mode

First, install PHP. You can only make it work with the Apache web server and its mod_php module. You will see, later in this document, in the FastCGI part (php-fpm) how to integrate PHP in Nginx and Apache.

Installation

The installation of PHP is relatively trivial since it consists of installing the main package and the few modules you will need.

This example installs PHP with the modules commonly installed with it:

sudo dnf install php php-cli php-gd php-curl php-zip php-mbstring

You can check that the installed version corresponds to the expected one:

php -v
PHP 8.3.19 (cli) (built: Mar 12 2025 13:10:27) (NTS gcc x86_64)
Copyright (c) The PHP Group
Zend Engine v4.3.19, Copyright (c) Zend Technologies
    with Zend OPcache v8.3.19, Copyright (c), by Zend Technologies

Configuration

Apache integration

To serve PHP pages in CGI mode, you must install the Apache server, configure it, activate it, and start it.

• Installation:

sudo dnf install httpd

* Activation:

sudo systemctl enable --now httpd
sudo systemctl status httpd

• Do not forget to configure the firewall:

sudo firewall-cmd --add-service=http --permanent
sudo firewall-cmd --reload

The default vhost should work right away. PHP provides a phpinfo() function that generates a summary table of its configuration. It is very useful to test the good working of PHP. However, be careful not to leave such test files on your servers. They represent a huge security risk for your infrastructure.

Create the file /var/www/html/info.php (/var/www/html being the default vhost directory of the default Apache configuration):

<?php
phpinfo();
?>

Use a web browser to check that the server works properly by going to the page http://your-server-ip/info.php.

Warning

Do not leave the info.php file on your server!

PHP-FPM (FastCGI)

As we highlighted earlier in this document, there are many advantages to switching web hosting to PHP-FPM mode.

Install php-fpm

To install the php-fpm package use:

sudo dnf install php-fpm

As php-fpm is a service from a system point of view, you must activate and start it:

sudo systemctl enable --now php-fpm
sudo systemctl status php-fpm

Configuration

php-fpm stores the main configuration file under /etc/php-fpm.conf:

include=/etc/php-fpm.d/*.conf
[global]
pid = /run/php-fpm/php-fpm.pid
error_log = /var/log/php-fpm/error.log
daemonize = yes

Note

The php-fpm configuration files are widely commented on. Go and have a look!

As you can see, the files in the /etc/php-fpm.d/ directory with the .conf extension are always included.

By default, php-fpm declares a PHP process pool named www in /etc/php-fpm.d/www.conf:

[www]
user = apache
group = apache

listen = /run/php-fpm/www.sock
listen.acl_users = apache,nginx
listen.allowed_clients = 127.0.0.1

pm = dynamic
pm.max_children = 50
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 35

slowlog = /var/log/php-fpm/www-slow.log

php_admin_value[error_log] = /var/log/php-fpm/www-error.log
php_admin_flag[log_errors] = on
php_value[session.save_handler] = files
php_value[session.save_path]    = /var/lib/php/session
php_value[soap.wsdl_cache_dir]  = /var/lib/php/wsdlcache

Instructions	Description
[pool]	Process pool name. The configuration file can comprise several process pools (the pool's name in brackets starts a new section).
listen	Defines the listening interface or the Unix socket used.

Configuring the way to access php-fpm processes

There are 2 ways to connect.

With an inet interface such as:

listen = 127.0.0.1:9000.

Or with a Unix socket:

listen = /run/php-fpm/www.sock.

Note

Using a socket when the web server and PHP server are on the same machine removes the TCP/IP layer and optimizes the performance.

When working with an interface, you have to configure listen.owner, listen.group, listen.mode to specify the owner, the owner group and the rights of the Unix socket. Warning: Both servers (web and PHP) must have access rights on the socket.

When working with a socket, you must configure listen.allowed_clients to restrict access to the PHP server to certain IP addresses.

Example: listen.allowed_clients = 127.0.0.1

Static or dynamic configuration

You can manage the processes of PHP-FPM either statically or dynamically.

In static mode, pm.max_children sets the number of child processes:

pm = static
pm.max_children = 10

This configuration will launch 10 processes.

In dynamic mode, PHP-FPM will launch at most the number of processes specified by the value of pm.max_children, starting by launching some processes corresponding to pm.start_servers, and keeping at least the value of pm.min_spare_servers of inactive processes and at most pm.max_spare_servers inactive processes.

Example:

pm = dynamic
pm.max_children = 5
pm.start_servers = 2
pm.min_spare_servers = 1
pm.max_spare_servers = 3

PHP-FPM will create a new process to replace one that has processed several requests equivalent to pm.max_requests.

By default, php-fpm sets pm.max_requests to 0, meaning processes are never recycled. Using the pm.max_requests option can be interesting for applications with memory leaks.

There is a third mode of operation, the ondemand mode. This mode only starts a process when it receives a request. It is not an optimal mode for sites with strong influences and you should reserve this for specific needs (sites with very weak requests, management backend, and so on).

Note

The configuration of the operating mode of PHP-FPM is essential to ensure the optimal functioning of your web server.

Process status

As with Apache and its mod_status module, PHP-FPM offers a page indicating the status of the process.

To activate the page, set its access path with the pm.status_path directive:

pm.status_path = /status

$ curl http://localhost/status_php
pool:                 www
process manager:      dynamic
start time:           03/Dec/2021:14:00:00 +0100
start since:          600
accepted conn:        548
listen queue:         0
max listen queue:     15
listen queue len:     128
idle processes:       3
active processes:     3
total processes:      5
max active processes: 5
max children reached: 0
slow requests:        0

Logging long requests

The slowlog directive specifies the file that receives logging of requests that are too long (for example, a file whose time exceeds the value of the request_slowlog_timeout directive).

The default location of the generated file is /var/log/php-fpm/www-slow.log.

request_slowlog_timeout = 5
slowlog = /var/log/php-fpm/www-slow.log

A value of 0 for request_slowlog_timeout disables logging.

NGinx integration

The default setting of nginx already includes the necessary configuration to make PHP work with PHP-FPM.

The configuration file fastcgi.conf (or fastcgi_params) is under /etc/nginx/:

fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;
fastcgi_param  REQUEST_SCHEME     $scheme;
fastcgi_param  HTTPS              $https if_not_empty;

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

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;

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

For nginx to process .php files, you must add the following directives to the site configuration file:

If PHP-FPM is listening on port 9000:

location ~ \.php$ {
  include /etc/nginx/fastcgi_params;
  fastcgi_pass 127.0.0.1:9000;
}

If php-fpm is listening on a Unix socket:

location ~ \.php$ {
  include /etc/nginx/fastcgi_params;
  fastcgi_pass unix:/run/php-fpm/www.sock;
}

Apache integration

The configuration of Apache to use a PHP pool is quite simple. You have to use the proxy modules with a ProxyPassMatch directive, for example:

<VirtualHost *:80>
  ServerName web.rockylinux.org
  DocumentRoot "/var/www/html/current/public"

  <Directory "/var/www/html/current/public">
    AllowOverride All
    Options -Indexes +FollowSymLinks
    Require all granted
  </Directory>
  ProxyPassMatch ^/(.*\.php(/.*)?)$ "fcgi://127.0.0.1:9000/var/www/html/current/public"

</VirtualHost>

Solid configuration of PHP pools

It is essential to optimize the number of served requests, and to analyze the memory used by the PHP scripts, to optimize the maximum amount of launched threads.

First of all, you need to know the average amount of memory used by a PHP process with the command:

while true; do ps --no-headers -o "rss,cmd" -C php-fpm | grep "pool www" | awk '{ sum+=$1 } END { printf ("%d%s\n", sum/NR/1024,"Mb") }' >> avg_php_proc; sleep 60; done

After a while, this should give us a pretty accurate idea of the average memory footprint of a PHP process on this server.

The result of the rest of this document is a memory footprint of 120 megabytes per process at full load.

On a server with 8 gigabytes of RAM, keeping 1 gigabyte for the system and 1 gigabyte for the OPCache (see the rest of this document), 6 gigabytes is left to process PHP requests from clients.

You can conclude that this server can accept at most 50 threads ((6*1024) / 120).

A good configuration of php-fpm specific to this use case would be:

pm = dynamic
pm.max_children = 50
pm.start_servers = 12
pm.min_spare_servers = 12
pm.max_spare_servers = 36
pm.max_requests = 500

with:

• pm.start_servers = 25% of max_children
• pm.min_spare_servers = 25% of max_children
• pm.max_spare_servers = 75% of max_children

Opcache configuration

The opcache (Optimizer Plus Cache) is the first level of cache on which we can influence.

It keeps the compiled PHP scripts in memory, which strongly impacts the execution of the web pages (removes the reading of the script on disk + the compilation time).

To configure it, we must work on:

• The size of the memory dedicated to the opcache according to the hit ratio, configuring it correctly
• The number of PHP scripts to cache (number of keys + maximum number of scripts)
• The number of strings to cache

To install it:

sudo dnf install php-opcache

To configure it, edit the /etc/php.d/10-opcache.ini configuration file:

opcache.memory_consumption=128
opcache.interned_strings_buffer=8
opcache.max_accelerated_files=4000

where:

• opcache.memory_consumption corresponds to the amount of memory needed for the opcache (increase this until you obtain a correct hit ratio).
• opcache.interned_strings_buffer the amount of strings to cache.
• opcache.max_accelerated_files is near to the result of the find ./ -iname "*.php"|wc -l command.

You can refer to an info.php page (including the phpinfo();) to configure the opcache (see for example the values of Cached scripts and Cached strings).

Note

At each new deployment of new code, it will be necessary to empty the opcache (for example by restarting the php-fpm process).

Note

Do not underestimate the speed gain that can be achieved by setting up and configuring the opcache correctly.

Author: Antoine Le Morvan

Contributors: Steven Spencer, Ganna Zhyrnova, Joseph Brinkman