Upgrade PHP to 8.0 on Ubuntu: Step-by-Step Guide

PHP 8.0 was released in November 2020 and brought the most significant language additions to PHP in years: a JIT compiler, named arguments, match expressions, the nullsafe operator, union types, and constructor property promotion. It also reached end-of-life in November 2023, meaning it no longer receives security patches.

This guide covers the exact steps to upgrade to PHP 8.0 on Ubuntu using the Ondrej Sury PPA — the standard third-party PHP repository that provides all PHP versions ahead of official Ubuntu package support. If you’re upgrading from PHP 7.4, this is the right next step; the guide assumes Apache or Nginx as your web server and covers both. If you’re on a fresh server or have flexibility on the target version, skip ahead to the PHP 8.4 upgrade guide — 8.4 is the current stable release and the better long-term choice for new deployments.

What’s New in PHP 8.0

• JIT compiler — PHP 8.0 introduced a Just-In-Time compiler as an experimental feature. For typical web applications (WordPress, Laravel, Symfony), JIT’s practical performance gain is modest — CPU-bound tasks see the most benefit. The more significant gains come from the engine optimisations that shipped alongside it.
• Named arguments — Function calls can now pass arguments by parameter name rather than position: array_slice(array: $a, offset: 1, preserve_keys: true). Useful for functions with optional parameters deep in the signature.
• Match expressions — An alternative to switch that returns a value, uses strict comparison (===), and has no fall-through behaviour. More concise and less error-prone than switch for value mapping.
• Nullsafe operator (?->) — Method chains and property accesses that short-circuit on null without nested null checks: $user?->getProfile()?->getAvatar().
• Union types — Type declarations can now accept multiple types: int|string, array|null. More flexible than the previous nullable-only syntax.
• Constructor property promotion — Properties can be declared and initialised directly in the constructor signature: public function __construct(public readonly string $name) {}.
• Attributes — Native PHP annotations via #[Attribute] syntax, replacing PHPDoc-based metadata conventions.
• New string functions — str_contains(), str_starts_with(), and str_ends_with() replace verbose strpos() checks for common string tests.

Before You Upgrade

Run this checklist before changing anything on a production server:

• Test on staging first. A PHP version change is the kind of change most likely to surface a compatibility issue in a plugin or custom code that looks fine until it runs. See how to set up a WordPress staging environment for the safe workflow — apply the upgrade there first and verify the site before touching production.
• Back up your database and files. Any time you’re changing server configuration, take a fresh backup first. A bad upgrade is recoverable from a backup; it’s much harder without one.
• Check your application’s PHP compatibility. WordPress 6.x requires PHP 7.4+ and recommends 8.0+, so moving to 8.0 is well within the supported range. For custom plugins or third-party code, check the developer’s stated PHP compatibility before upgrading.
• Note your current extension list. Run php -m on the server to list all active PHP modules. You’ll reinstall extensions for PHP 8.0; knowing what’s active now means you won’t miss one.

Step 1: Check the Current PHP Version

Confirm what’s currently running before making changes:

php -v

On Apache with multiple PHP versions, the CLI version and the web server version can differ. To check which PHP version Apache is serving, create a temporary info file:

echo '<?php phpinfo(); ?>' | sudo tee /var/www/html/phpinfo.php

Load http://your-server-ip/phpinfo.php in a browser and look at the PHP Version line. Delete the file immediately after checking — it exposes server configuration publicly:

sudo rm /var/www/html/phpinfo.php

Step 2: Add the Ondrej Sury PPA

Ubuntu’s official package repositories don’t carry all PHP versions promptly. The Ondrej Sury PPA is the standard source for PHP packages on Ubuntu — it’s maintained by the Debian PHP maintainer and is widely used in production environments:

sudo apt install software-properties-common -y
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update

If you’ve previously run this PPA for an earlier PHP version, the add-apt-repository line may report that the PPA is already configured — that’s fine, run sudo apt-get update and continue.

Step 3: Install PHP 8.0 and Extensions

Install the PHP 8.0 interpreter:

sudo apt install php8.0 -y

Then install the extensions. This set covers WordPress and most PHP web applications:

sudo apt install php8.0-common php8.0-mysql php8.0-xml php8.0-xmlrpc php8.0-curl php8.0-gd php8.0-imagick php8.0-cli php8.0-dev php8.0-imap php8.0-mbstring php8.0-opcache php8.0-soap php8.0-zip php8.0-intl -y

For sites using Redis as an object cache, also install:

sudo apt install php8.0-redis -y

Compare this list against the output of php -m you noted earlier and install any additional extensions your application requires.

Step 4a: Switch Apache to PHP 8.0

If you’re running Apache with mod_php, disable the current PHP module and enable the PHP 8.0 one:

sudo a2dismod php7.4
sudo a2enmod php8.0
sudo service apache2 restart

Replace php7.4 with whichever version is currently active if you’re coming from a different version. After restarting, verify Apache is using PHP 8.0 by checking the server info or running:

php -v

Step 4b: Switch Nginx to PHP 8.0 (PHP-FPM)

Nginx doesn’t use mod_php — it communicates with PHP via FastCGI (PHP-FPM). Install the PHP 8.0 FPM package:

sudo apt install php8.0-fpm -y
sudo systemctl enable php8.0-fpm
sudo systemctl start php8.0-fpm

Update your Nginx site configuration to point to the PHP 8.0 FPM socket. In your server block, change the fastcgi_pass directive:

# Change from:
fastcgi_pass unix:/run/php/php7.4-fpm.sock;

# To:
fastcgi_pass unix:/run/php/php8.0-fpm.sock;

Then test the Nginx config and reload:

sudo nginx -t
sudo systemctl reload nginx

You can also stop the old FPM service if you no longer need it:

sudo systemctl disable php7.4-fpm
sudo systemctl stop php7.4-fpm

Step 5: Verify the Upgrade

Check the PHP CLI version:

php -v

The output should show PHP 8.0.x. If the CLI still reports an older version, update the system-wide PHP CLI alternative:

sudo update-alternatives --config php

This command lists all installed PHP versions and lets you select the default. Enter the number corresponding to PHP 8.0 and press Enter.

After updating, confirm with php -v again. Also verify your web server is serving PHP 8.0 by checking the response headers or a temporary phpinfo() page as described in Step 1.

Troubleshooting

Apache shows a 500 error after the module switch: Check the Apache error log (sudo tail -f /var/log/apache2/error.log). A common cause is a PHP extension that’s installed for the old version but not yet for 8.0. Re-run the extension install command in Step 3 and restart Apache.

Nginx returns a 502 Bad Gateway: PHP-FPM isn’t running or the socket path is wrong. Run sudo systemctl status php8.0-fpm to check. If it’s not running, sudo systemctl start php8.0-fpm. If the socket path differs from what’s in your Nginx config, check the actual socket path: ls /run/php/.

WordPress admin shows a white screen after the upgrade: Enable WordPress debug mode (define('WP_DEBUG', true); in wp-config.php) and reload the page to see the error output. Usually a plugin compatibility issue — deactivate plugins one at a time to isolate the cause. See the WordPress white screen of death fix guide for the full diagnostic workflow.

The PHP Upgrade Series for Ubuntu

PHP 8.0 reached end-of-life in November 2023. If you’ve just arrived here from PHP 7.4, upgrading to 8.0 as an intermediate step is reasonable when an application’s compatibility floor requires it — but plan to continue to a supported version promptly. The recommended path:

• PHP 7.4 → PHP 8.0: this guide
• PHP 8.0 → PHP 8.2: PHP 8.2 upgrade on Ubuntu (security support until December 2026)
• PHP 8.0 → PHP 8.4: PHP 8.4 upgrade on Ubuntu (current stable release, recommended for new deployments)
• PHP 8.4 → PHP 8.5: PHP 8.5 upgrade on Ubuntu

The process for each step is the same as above — swap the version number in every command. Extension availability via the Ondrej Sury PPA is consistent across all versions on Ubuntu 20.04 LTS and 22.04 LTS.

For PHP upgrades on a WordPress site, keeping WordPress and its plugins current alongside the PHP upgrade reduces compatibility risk significantly. See how to update WordPress safely for the recommended update sequence.