As of May 15th, 2022, with the release of Backdrop CMS version 1.22.0, Backdrop CMS will require PHP version 5.6 or greater.
Currently, the listed requirement for Backdrop CMS is PHP 5.3.29 or greater, a version of PHP that has long since reached the end of its official life.
Philosophically, the Backdrop community aspires to maintain as much backward compatibility as possible and is committed to running on affordable hosting with very basic requirements. Our policy has been to support the oldest still-supported version of PHP provided by a Linux distribution. With the waning popularity and recent discontinuation of the CentOS distribution, we have decided to make this change a bit earlier than previously expected, as CentOS7 is now the only Linux distribution supporting PHP versions older than 5.6, and very few websites run on CentOS7.
If your Backdrop site is running on a version of PHP older than 5.6, please look into options for upgrading or moving to a new server. Your site admin can find the version of PHP your site is using on the Status Report page (/admin/reports/status). Before upgrading PHP, make sure that you have upgraded to the most recent version of Backdrop Core and that all of your contributed modules and themes are up to date. Backdrop Core is compatible with PHP 8.0.
The benefits of this change to the Backdrop CMS community include:
- It is easier for us to keep Backdrop up to date if we don't have to ensure that all changes are compatible with so many versions of PHP.
- Newer versions of PHP are more secure.
- We will now have the ability to use these PHP features that previously would have broken sites running on outdated versions of PHP
- Short array syntax
- Traits: https://www.php.net/traits
- Generators: https://www.php.net/generators
- The finally keyword for try/catch sections: https://www.php.net/manual/en/language.exceptions.php#language.exception...
- Variable length argument lists: https://www.php.net/manual/en/functions.arguments.php#functions.variable...
- Calling empty() on callables instead of just variables
- List of new features in 5.6: https://www.php.net/manual/en/migration56.new-features.php
How does this affect Backdrop CMS sites running on older versions of PHP?
Beginning with version 1.22.0 of Backdrop CMS on May 15th, 2022, we may include code changes in Backdrop core that will break sites running on versions of PHP prior to 5.6. You will still be able to run Backdrop on older versions of PHP as long as you do not update your site. Failure to update your Backdrop site will mean missing out on new bug fixes, feature improvements, and security updates.
If you have questions about this change, please post a question in the forum.