Please note that according to the PHP version support timelines, PHP 5.6.40 might be the last scheduled release of PHP 5.6 branch only if no security issues arises, otherwise there will be additional release for PHP 5.6 branch. Hence if your PHP installation is based on PHP 5.6 or PHP 7.0 then we would recommend you to upgrade to latest PHP 7.1 or PHP 7.2 or PHP 7.3 versions.
Let us know in the comments if you are facing any issues with upgrade, we will definitely try to answer as many as we can.