In this article, I will explain ionCube and recommended version:
What is ionCube: ionCube was created in 2002, and gave developers tools to protect software written in the PHP programming language from being viewed, edited and ran on unlicensed computers. The tools use a technique of compiling the bytecode prior to encoding so that the source code is eliminated, and runtime overheads are reduced. A PHP extension called the ionCube Loader handles the reading and execution of encoded files at runtime.
Which version is recommended: We recommend ionCube PHP Loader v5.0+
How can I check If it's installed or not: You can check PHP Info page to check this or, you can run a simple command "php -v" on terminal to check this.
How to get it: You can contact your hosting provider to install it for you or, you can install it by downloading from - https://www.ioncube.com/loaders.php