It's now time to run your Joomla site on at least PHP 7.1. as PHP 7.0 has reached its end of life and is no longer being developed or supported, except for security updates for a few more months. How to change the PHP version your Joomla site is running on is what today's Maintenance Monday is all about.
If you are getting the following warning on your Joomla Admin console, this tutorial will help you: "Warning Your PHP version, 7.0.31, is only receiving security fixes at this time from the PHP project. This means your PHP version will soon no longer be supported. We recommend planning to upgrade to a newer PHP version before it reaches end of support on 2018-09-03.
Joomla will be faster and more secure if you upgrade to a newer PHP version (PHP 7.x is recommended). Please contact your host for upgrade instructions."