Excellent.
If you ask for a Rocket account & come & test & talk to us we can help, and you can help us test.
There are various ways of using older php.
CentOS7 has php 5.4 by default which will be supported for the lifetime of CentOS7.
With php-fpm you can use other versions, including php 8....
Really would suggest you stick to supported versions only though, for your own security.
So 5.4, and php-fpm 7.3 (until Dec 202) or preferably 7.4+
You really should be upgrading systems though. Yup. It's a pain in the butt. I hate rapid release..... Hey ho.