The pages of your website include text, images and other data are managed using the concrete5 content management system. The look and feel of your site is controlled by a concrete5 Theme that was probably developed specifically for you. A scripting language called PHP provides underlying functionality and security and is installed on your web server. These three elements should be considered together when planning the upgrades needed to keep your website performant and secure:
concrete5/Concrete CMS
Like all modern web applications concrete5 (now Concrete CMS) uses third-party components that are constantly updated to improve performance and security. Changes to these components and to Concrete CMS itself are released regularly as subversion updates. From time to time a major release is necessary to deliver significant changes and improvements (Version 8 was first released in January 2016) .
There is a direct upgrade path from concrete5 8.x.x to Concrete CMS version 9 but to run properly it is necessary that your website theme, any custom code and any third party packages are updated to be compatible.
Timing: concrete5 version 8 will be EOL (end of life) from 31st December 2022. This means there will be no functionality updates after then. Critical security updates for Concrete v8.x will continue to be issued during 2023.
PHP
Concrete CMS Version 9 runs on PHP8 the latest and most secure version of the server side scripting language.
Earlier versions of concrete5 do not support PHP8 and will only run on PHP7.
Timing: PHP7 is officially EOL at the end of November 2022. However it is widely anticipated that various groups will make security upgrades available after this date.
Your Theme and other custom code
With Concrete CMS Version 9 release 9.2 coming soon and PHP 8.1 now available the only barrier to having the latest versions running your website will be the need to update custom code developed specifically for you within your website theme or elsewhere and to update any third party packages your website uses.
Options for Theme updates
Your website Theme is likely to use an established theme framework like Foundation or Bootstrap to ensure compatibility with the widest range of devices. Concrete CMS Version 9 is more closely linked with the theme framework than previously and now uses Bootstrap 5 to format default blocks. This means that themes that using Bootstrap 5 will provide greater compatibility with Concrete CMS and allow you to use the new block types in Concrete CMS without the need for further theme development.