PHP 8.4 Installation and Upgrade guide for Ubuntu and Debian

PHP 8.4 brings several new features, security improvements, and performance improvements with healthy amounts of feature deprecations and removals.

This guide explains how to install PHP 8.4 or upgrade to PHP 8.4 on Ubuntu, Debian, or their derivatives. Although it is possible to compile PHP from source, installing it from an APT repository as explained below is often faster and more secure because these repositories will provide the latest bug fixes and security updates in the future.

PHP 8.4 is not available in current Debian and Ubuntu software repositories. This guide uses the repositories maintained by Ondřej Surý. Ondrej's PHP repositories have been the de-facto repositories for PHP on Ubuntu, Debian, and their derivatives for several years.

Potential Backward Compatibility Impact in PHP 8.4

PHP 8.4 brings several new features such as property hooks, asymmetric visibility, improvements in DOM, Curl, PCRE extensions, and more.

However, PHP 8.4 also deprecates some PHP functionality and removes four PHP extensions from PHP core to PECL. This can affect existing PHP applications to emit additional PHP notices/warnings, or fail in certain conditions.

Some of the notable changes that are likely to affect existing applications include:

• Implicitly nullable parameter declarations deprecated
• E_STRICT constant deprecated
• Extensions moved from PHP core to PECL: Pspell, IMAP, OCI8, and PDO_OCI.

When a PHP extension is moved from PHP core to PECL, the extension will follow its own release cycle. The repositories used in the guide will provide updates for them if the PECL project for that extension releases updates. However, this also means the PECL extension can (and often does) fall behind on maintenance.

Before continuing, make sure to backup the system. This guide installs PHP 8.4 side-by-side along any existing PHP installations, which offers an easy way to switch back to the other PHP installation if necessary.

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This step only applies when upgrading an existing PHP setup. The following command lists all installed PHP packages with the text php in its name, shows it on screen, and writes it to a file called packages.txt. This file comes in handy at a later step when installing the PHP 8.4 packages, to ensure the same list of PHP 8.4 versions of the extensions are installed.

dpkg -l | grep php | tee packages.txt

2. Add ondrej/php PPA/DPA

Because PHP 8.4 packages are not available in any of the current Debian or Ubuntu software repositories, the PHP packages must come from another repo.

Ondřej Surý maintains a package archive that contains compiled binaries of all current PHP versions, for Ubuntu and Debian. It also ships several PECL extensions including PECL extensions for PHP core extensions unbundled in PHP 8.4.

Once this repository is added, the initial installation and updates can be done with the standard apt commands.

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Ubuntu PPA

dpkg -l | grep php | tee packages.txt

Debian DPA

sudo LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php # Press enter to confirm.sudo apt update

3. Install PHP 8.4 Server API packages

In the Ondrej's PPA and DPA, PHP 8.4 packages follow the php8.1-NAME pattern. PECL and shared PHP extensions also follow the same pattern.

Before installing PHP extensions, make sure to install one of the following PHP Server API (SAPI) packages:

Install PHP-CLI only

To install PHP CLI, install the php8.1-cli package, along with the extensions desired.

sudo apt-get updatesudo apt-get -y install lsb-release ca-certificates curl apt-transport-httpssudo curl -sSLo /tmp/debsuryorg-archive-keyring.deb https://packages.sury.org/debsuryorg-archive-keyring.debsudo dpkg -i /tmp/debsuryorg-archive-keyring.debsudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/deb.sury.org-php.gpg] https://packages.sury.org/php/ $(lsb_release -sc) main" > /etc/apt/sources.list.d/php.list'sudo apt-get update

PHP-CLI and PHP as an Apache module

To install PHP CLI and PHP 8.4 as an Apache module, install the libapache2-mod-php8.4 package:

sudo apt install php8.4-cli

Unless the PHP application requires PHP to be installed as an Apache module, consider installing PHP-FPM instead.

PHP CLI and PHP-FPM (recommended)

It is recommended to install PHP-FPM to integrate PHP with web-servers such as Apache, Nginx, and Caddy.

sudo apt install php8.4-cli libapache2-mod-php8.4

This installs the php8.4-fpm service and automatically enables it. See the FPM web-server integration section for the additional steps required later.

5. Check Installation

For a quick check of the PHP installation, run the following:

sudo apt install php8.4-cli php8.4-fpm

It should show the PHP version, build time, and more information:

`php -v` output

If the PHP-FPM service is installed, its status can be checked as follows:

php -v

If the PHP-FPM server is running successfully, it should show an output similar to below:

`systemctl status php8.4-fpm` output

4. Install PHP Extensions

All of the shared PHP extensions and PECL extensions follow the php8.4-EXTNAME pattern, where extname is the name of the extension.

When upgrading an existing system, refer to the packages.txt file created in the first step to check the existing PHP 8.3 or older PHP extensions.

To install a PHP extension, use the apt install command with the PHP extension name with the php-8.4- prefix. For example, the gd extension is installed with the php8.4-gd package:

sudo systemctl status php8.4-fpm

The following command installs a set of most common PHP extensions required by a majority of PHP libraries and frameworks:

sudo apt install php8.4-gd

To search for additional PHP extensions, use the apt search command:

dpkg -l | grep php | tee packages.txt

Development Tools

Development tooling such as Xdebug and code coverage tools can also be installed following the same package naming convention.

This step is not recommended on production servers.

Xdebug

sudo LC_ALL=C.UTF-8 add-apt-repository ppa:ondrej/php # Press enter to confirm.sudo apt update

PCOV

sudo apt-get updatesudo apt-get -y install lsb-release ca-certificates curl apt-transport-httpssudo curl -sSLo /tmp/debsuryorg-archive-keyring.deb https://packages.sury.org/debsuryorg-archive-keyring.debsudo dpkg -i /tmp/debsuryorg-archive-keyring.debsudo sh -c 'echo "deb [signed-by=/usr/share/keyrings/deb.sury.org-php.gpg] https://packages.sury.org/php/ $(lsb_release -sc) main" > /etc/apt/sources.list.d/php.list'sudo apt-get update

5. Web Server Integration

Depending on the server API installed in step 3, web server integration might require additional configuration for the PHP 8.4 upgrade to take effect.

PHP-FPM

When using PHP-FPM (by installing the php8.4-fpm package), the web server needs to be reconfigured to communicate with the PHP 8.4 FPM server over the updated the socket path.

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Apache: This configuration change is made easy by switching on the PHP 8.4 configuration file:

sudo apt install php8.4-cli

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Nginx: Update the fastcgi_pass directive from the old PHP FPM socket path to the new PHP 8.4 path:

sudo apt install php8.4-cli libapache2-mod-php8.4

See Nginx documentation for more information

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Caddy Server: Update the reverse_proxy directive to use the new PHP 8.4 FPM server socket path:

sudo apt install php8.4-cli php8.4-fpm

See How to use Caddy Server with PHP for more configuration details.

PHP as an Apache module

If PHP is installed as an Apache module, the following command disables the previous PHP module (8.3 in this example) and enables the new PHP version:

php -v

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