Starting from tomorrow PHP 5.6. will not be actively supported anymore. Sebastian Bergmann, author of PHPUnit explains how PHP's release process works, and what the ending of active support means for you. Spoiler: you should upgrade asap.

It is high time to think about upgrading your PHP stack to PHP 7, ideally to PHP 7.1. This should be a short-term goal for you. Upgrading the version of PHP you use must not be a rare event you are afraid of. You must not think of upgrading your PHP stack as a "special project". You need to make upgrading the PHP version you use part of your normal operational procedure and align the upgrade cycle of your PHP stack with the release cycle of the PHP project. This should be a long-term goal for you.

https://thephp.cc/news/2016/12/php-5-active-support-ends-now-what