I was just allowed to update the PHP version on a web server and would like to share the procedure with you here.
With this procedure, I was able to carry out an update within the 7.x releases without any problems. I have also carried out a test update from version 7.4 to PHP8.1. The test page still works without any problems.

The following commands have been executed on a CentOS 8 stream installation and will work on all RHEL-based systems or with the package manager dnf.

Installing the necessary repos

First we need to install the necessary repos for the update. To do this, we simply run the following commands and confirm the installation:

dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
dnf install https://rpms.remirepo.net/enterprise/remi-release-8.rpm
dnf clean all
dnf makecache
  1. the EPEL repo contains, as the name suggests, many Extra Packages for Enterprise Linux .
  2. the REMI repo is the repository for PHP packages.
  3. dnf clean all throws away the cache of dnf once.
  4. dnf makecache will then rebuild it... can be done without dnf clean all, but who cares ­čśÇ

Swap modules

Now we exchange the modules once. For this we also use the dnf power ­čÖé

A short warning at this point, with mayor release changes problems can occur here, this should definitely be tested beforehand.
Also, a backup is always a good idea that should be implemented!

Update: I have carried out an update from PHP7.4 to PHP8.1. It went through without any problems.
What are your experiences? Feel free to write it in the comments!

## Lists of available PHP modules
dnf module list php
## If a module is already activated, it must be reset beforehand.
dnf module reset php
## Select the new module
dnf module enable php:remi-8.0

UPDAAAAATE!!!!!111elf

Finally, all that's missing is the update and we're done!

dnf update