If you are still using PHP 7.1 after the community support is officially dropped in December, you can either upgrade your PHP applications to 7.3 to retain community support, or you take the risk for security breaches and downtimes if you want to keep your applications on PHP 7.1. Or there is a third option, you can keep your applications on PHP 7.1 and get long-term support via Zend Server.
By running Zend Server, you can get the level of support you need for the PHP 7.1 applications. The enterprise PHP platform includes a certified PHP stack and comprehensive tools for web application development.
A certified PHP 5.6 or 7.1 runtimes are included in Zend Server. Zend Server supports the certified PHP runtime for five years from the release date. This means two years after the community support has ended. As a part of the support, Zend provides bug fixes and security updates for the duration of the full support.
Source: Official Website of Zend