PHP is the programming language that WordPress is made from, and it needs to be current in order to keep your website’s code secure.
Many WordPress websites use PHP 7.4, or an earlier version. Security support for PHP 7.4 is ending on November 28, 2022. This is an internet-wide phenomenon.
https://www.php.net/supported-versions.php
Almost all web hosts will require your site's PHP version to be upgraded to PHP 8 before then. Your host may upgrade your PHP version automatically, which might cause your site to break.
The best thing to do is test your site with PHP 8 as early as possible, so you have time to address any problems before the Nov 28 deadline.
In this informal presentation, we will discuss the best practices for approaching the PHP upgrade. We'll review what different hosting providers are recommending, and how you can safely test PHP 8 on your site before the deadline, whether on a staging site or a local development environment. We'll talk about what might break, and how you can find and resolve any errors that occur.