PHP is stopping security updates of PHP 5.6 on 31 Dec and PHP 7.0 on 3 Dec which means that on those dates we can no longer reliably support those versions of PHP.
OpenEMR will be dropping support for PHP ≤ 7.0 at the end of 2018. A release number has yet to be announced.
See http://php.net/supported-versions.php for details.