Convert Website operating on PHP 7.4 to PHP 8.4

3 years ago our website was updated from PHP 5.3 to be able to operate on PHP 7.4

The specs for that project required full function up to PHP 8.2.

My Internet host is now requiring us to upgrade our PHP to 8.4

This project is to upgrade our code to operate on PHP 8.4 and for all functions to remain operational.

It is possible that no changes will be required to the code, but it will be up to you to verify that.

The website must remain fully operational during the work, as it does right now.

-The finished pages should all meet W3C validator standards with no errors shown on any of our website pages.
-It must continue to display properly on Safari, Chrome, and IE browsers, including the mobile version of the website.

Some specific areas of concern that will be verified are:
-Payment integration with PayPal
-Admin functions for making updates to the website
-Auto e-mail function for a sign up on our website.
-Scrollers still operational.
-there should be no differences in the web page layout upon completion.

We are not requesting any other changes be made to this website.