PHP selection and FPM pools #

This page is for system administrators and support staff at hosting companies who choose and configure PHP for Exponential sites on panel servers. It answers which PHP versions to offer, why the command line PHP matters as much as the web PHP, how a PHP-FPM pool for an Exponential site should look, and how to reload the right PHP after a change, which on servers with several PHP versions is the most common mistake.

Contents #

1. Which PHP versions to offer
2. Web PHP and command line PHP
3. One pool per site
4. Pool settings for Exponential
5. OPcache
6. Reloading the right PHP-FPM
7. Restrictions panels often set
8. Checklist

Which PHP versions to offer #

From 2.2 PHP:

"Use the newest PHP your system offers: each version brings speed, and the older ones lose security support first." 64-bit PHP is recommended "for support of more than 30 languages".

Web PHP and command line PHP #

"Exponential uses PHP twice: the web server's PHP (PHP-FPM, mod_php or Velocity's workers) serves pages, and the command line PHP (php) runs Composer, the installers, the console, the cronjobs and Velocity itself. Both must be of a supported version and have the same extensions. On machines with several PHP versions (Plesk, Remi) the php on the PATH is often not the one the web server uses." (Command line and web PHP)

What goes wrong when they differ: Composer picks package versions the web PHP cannot run, or an install succeeds on the command line and the browser shows a white page.

php -v; php -m                       # the PATH's PHP
/opt/plesk/php/8.5/bin/php -v        # a Plesk PHP by its path
php --ini                            # the files the command line PHP reads

Compare with the web side on Setup > System information, which "first says which server answered" and how it runs PHP (System information).

One pool per site #

• "The pool runs PHP as the site's user" (8.5.2).
• When "several customers on one machine need operating-system isolation from each other", use "a traditional server with one PHP-FPM pool per site" (8.1).
• Everything that writes var/ (pool, cron, console, Velocity workers) runs as that one user (8.7.2).

Where pools live, per the sources:

Sources: Chapter 2, Plesk and Debian, Velocity engines, Which PHP-FPM.

Pool settings for Exponential #

"Settings of interest for Exponential (in the pool file or php.ini): memory_limit (at least 256M; more for large imports), max_execution_time, upload_max_filesize and post_max_size (your largest upload), OPcache on." (8.5.2)

Chapter 2 gives "a minimal set for a production php.ini (or a PHP-FPM pool's php_admin_value lines)":

memory_limit = 256M
max_execution_time = 60
date.timezone = Europe/Berlin
file_uploads = On
upload_max_filesize = 64M
post_max_size = 64M
allow_url_fopen = On
variables_order = "EGPCS"

"The values above the minimums are suggestions, not requirements." The setup wizard's floors are memory_limit 64M and max_execution_time 30 (2.5).

Request time limits. Apart from max_execution_time, a pool can kill a request after a wall-clock limit (request_terminate_timeout), which PHP's set_time_limit() cannot override. The MongoDB porting notes describe the setup wizard being cut off by it and raising it for the install only (MongoDB kernel support). Under Velocity the equivalent is the engine's requestTimeout (30 seconds; the client gets 504); keep SQLite's SQLiteTransactionWait (default 25) below the request timeout (9.2).

OPcache #

Under PHP-FPM, enable OPcache in the pool's php.ini, and keep timestamp checks on: "Never set opcache.validate_timestamps=0 on an Exponential site: a cache file rewritten after a clear would be served in its old form until PHP restarts." (10.12 OPcache)

opcache.enable=1
opcache.memory_consumption=256
opcache.max_accelerated_files=20000
opcache.interned_strings_buffer=32
opcache.validate_timestamps=1
opcache.revalidate_freq=2

Velocity sets its own OPcache options in settings/velocity.ini [PHPSettings] IniOptions[]; see OPcache.

Reloading the right PHP-FPM #

"After a PHP class, operator or INI change, reload the FPM master that serves the site" (8.5.2). "On machines with several PHP versions the master serving the site is often not the one called php-fpm. Find it by its pool file."

exp:velocity deploy does this for you. [DeploySettings] PhpFpmService=auto (the default in settings/velocity.ini) finds "the pool configuration named after the installation's hosting domain (/var/www/vhosts/<domain>/..., as Plesk names pools) or one that names the installation's directory" in the four pool directories above. "The step is a reload, so no request is dropped. It needs root" (Velocity engines).

php bin/php/console exp:velocity deploy --dry-run --allow-root-user                # shows which service it found
php bin/php/console exp:velocity deploy --no-velocity --allow-root-user            # Apache/nginx site: caches + FPM reload

Set PhpFpmService to the service name to fix it, or to disabled when Velocity serves the site alone.

Restrictions panels often set #

Checklist #

• To do: PHP 8.0 or later offered (8.0 only for sites that run 6.0.15 or later; Velocity needs 0.0.4.54 or later on it).
• To do: Same version and extensions for web and command line; cron and PhpCliPath follow PHP version changes.
• To do: One pool per site, running as the site's user.
• To do: Pool settings and OPcache as above; validate_timestamps on.
• To do: exp:velocity deploy --dry-run names the right PHP-FPM service.
• To do: Panel restrictions documented with their effects.

Demo mode in a pool. A public demo can get its environment variable from its own pool: env[EXP_DEMO_MODE] = 1 (it works with clear_env = yes), then reload that version's master. Never in a pool other sites share. Demo mode for hosts, php-fpm-pool-demo.conf.

Related pages #

• Control panels: overview, Plesk
• PHP versions and extensions, PHP settings for Exponential
• PHP-FPM tuning, Per-customer users and pools
• Free documentation: this page is free to copy, translate and improve under the GNU FDL 1.3.