Hi all

Recently, I helped one of my clients who was using an Amazon Lightsail WordPress instance provided by Bitnami. Bitnami is advantageous in that it provides a fully working stack, so you don’t have to worry about configuring LAMP or environments. You can find more information about the Bitnami Lightsail stack here.

However, the client’s stack was using the latest PHP 8.x version, while the WordPress site he runs uses several plugins that need PHP 7.4. I advised the client to consider upgrading the website to support the latest PHP versions. However, since that would require a lot of work, and he wanted the site to be up and running, he decided to downgrade PHP.

The issue with downgrading or upgrading PHP on a Bitnami stack is that it’s not possible. Bitnami recommends launching a new server instance with the required PHP, MySQL, or Apache version and migrating the data over. So, I decided to do it manually.

Here are the server details:

Debian 11
Current installed PHP: 8.1.x

Upgrading or downgrading PHP versions on a Bitnami stack is essentially the same as on a normal Linux server. In short, you need to:

Ensure the PHP packages for the version you want are installed.
Update any configuration for that PHP version.
Update your web server configuration to point to the correct PHP version.
Point PHP CLI to the correct PHP version.
Restart your web server and php-fpm.

What we did was install the PHP version provided by the OS. Then, we updated php.ini to use the non-default MySQL socket location used by the Bitnami server. We created a php-fpm pool that runs as the “daemon” user. After that, we updated the Apache configuration to use the new PHP version.

1. Make sure packages for your target version of PHP are installed
To make sure that the correct packages are available on your system for the PHP version you want, first make sure your system is up to date by running these commands:

sudo apt update
sudo apt upgrade
If it prompts you to do anything with config files, usually, you should just go with the default option and leave the current config as-is. Then, install the packages you need. For example, you can use the following command to install common PHP packages and modules:
sudo apt install -y php7.4-cli php7.4-dev php7.4-pgsql php7.4-sqlite3 php7.4-gd php7.4-curl php7.4-memcached php7.4-imap php7.4-mysql php7.4-mbstring php7.4-xml php7.4-imagick php7.4-zip php7.4-bcmath php7.4-soap php7.4-intl php7.4-readline php7.4-common php7.4-pspell php7.4-tidy php7.4-xmlrpc php7.4-xsl php7.4-fpm

2. Make sure PHP configuration for your target version is updated
Find the mysql socket path used by your Bitnami stack by running this command:

# ps aux | grep –color mysql.sock
mysql 7700 1.1 2.0 7179080 675928 ? Sl Mar21 11:21 /opt/bitnami/mariadb/sbin/mysqld –defaults-file=/opt/bitnami/mariadb/conf/my.cnf –basedir=/opt/bitnami/mariadb –datadir=/bitnami/mariadb/data –socket=/opt/bitnami/mariadb/tmp/mysql.sock –pid-file=/opt/bitnami/mariadb/tmp/mysqld.pid

Edit php.ini file

vi /etc/php/7.4/fpm/php.ini


; Default socket name for local MySQL connects. If empty, uses the built-in
; MySQL defaults.

Replace with

; Default socket name for local MySQL connects. If empty, uses the built-in
; MySQL defaults.
pdo_mysql.default_socket= “/opt/bitnami/mariadb/tmp/mysql.sock”


mysqli.default_socket =

Replace with

mysqli.default_socket = “/opt/bitnami/mariadb/tmp/mysql.sock”

Create a php-fpm pool file

vi /etc/php/8.1/fpm/pool.d/wp.conf

env[PATH] = $PATH

Feel free to adjust the PHP FPM settings to match your server specifications or needs. Check out this informative article for more tips on optimizing PHP FPM performance. Just keep in mind that Bitnami configures their stack with the listen.owner and listen.group settings set to daemon.

This pool will listen on unix socket “/opt/bitnami/php/var/run/www2.sock”.

Enable and restart PHP 8.1 fpm service

systemctl enable php7.4-fpm
systemctl restart php7.4-fpm

3. Update your web server configuration to point to the correct PHP version

Edit file

vi /opt/bitnami/apache2/conf/bitnami/php-fpm.conf

For some installations, file is located at

vi /opt/bitnami/apache2/conf/php-fpm-apache.conf

Inside you file find

SetHandler “proxy:fcgi://www-fpm”

Find and replace www.sock with www2.sock

4. Make sure PHP-CLI points to the right PHP version

Rename the default PHP installed by bitnami.

mv /opt/bitnami/php/bin/php /opt/bitnami/php/bin/php_8.1_bitnami.

create a symlink from newly installed PHP 7.4

ln -s /usr/bin/php7.4 /opt/bitnami/php/bin/php

Test the installed version by running below command
~# php -v
PHP 7.4.33 (cli) (built: Feb 22 2023 20:07:47) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
with Zend OPcache v7.4.33, Copyright (c), by Zend Technologies

5. Restart PHP-FPM and your webserver

sudo systemctl restart php7.4-fpm; sudo /opt/bitnami/ctlscript.sh restart apache