Why you need to upgrade PHP

The most obvious reason to upgrade php is security! Older versions are more likely to have security vulnerabilities and outdated code that is not longer supported.

Newer versions may support new features and functionality great for web development. It usually includes performance improvements to make your website load faster!

And, you can generally expect to see a decrease in memory usage when upgrading php from older to newer versions, which is really helpful for server with small amount of RAM.
Step 1: Install PHP 8.4 in Ubuntu 22.04 | 24.04

PHP 8.4 is easy to install in all current Ubuntu LTS releases through Ondrej Sury’s PPA, which is practically “official”, as the maintainer also manages the official php package in Debian.