I have forms on several website in our VPS,

And in our VPS, today we currently use the PHP 5 version, we would like to change the entire structure of our local server to use in cpanel the stable version of PHP 7.

Https://blog.cpanel.com/php-7-is-here/

If I change to version 7, the old sites developed by the incomedia software, website x5 v12 and v13, may not work the forms and functions that use php 5?

Or am I going to have to rewrite all the old sites to work in version 7?

"In short, I want to change my server from PHP 5 to 7" the files and codes generated by the website x5 will work normally?

I await a brief reply.