001 Install PHP 8.x
It turns out, since PHP is so popular, there are lots and lots of options of how to install it. There are too many options to cover everything, so here are links to some of the plethora of installation guides available on the web along with a few recommendations to consider:
Linux
Linux and other *nix distributions are usually listed last, if at all, in these sorts of write-ups. As it happens, Linux is amazing, so it will go first here.
Installation Options
Package manager
Solaris, BSD, other
Our choice: APT or YUM
We like APT or YUM because they are Debian and Red Hat package managers. Those are widely used distros with proven and well used resources. Specifically, we like Ubuntu and Fedora as those are the most popular distros that use apt and yum, respectively. We like APT or YUM because of how simple it is to install packages. Of course, google around if these resources don't work for you. Try to find a guide that will help you install the latest version of PHP.
ThisHosting.Rocks - How to install PHP on Ubuntu
Digital Ocean - Lamp Stack install
Vultr Docs - Get PHP along with Apache webserver.
nestify - Install PHP in Fedora 27 (along with Apache and MariaDB)
Mac
Options
Our choice: Homebrew
Mac comes with PHP pre-bundled. That can work in a lot of instances; however, it is several versions behind the most recent, and in the PHP world, as in most software technologies, there are some big differences in those versions. There are lots of options to get PHP on a Mac, but we like homebrew because of how simple it is to use and how similar it is to Linux package managers. Finally, we prefer homebrew because we haven't tried many other options.
Grav - macOS 11.0 Big Sur Apache Setup: Multiple PHP Versions
Romans Malinovskis - (from 2018) Install PHP 7.3 + xdebug on MacOS Catalina (with homebrew)
Windows
Options
BitNami
Manual install - see https://windows.php.net and https://www.php.net/download
Our choice: XAMPP
It is pretty easy to get PHP onto windows using the windows binaries available on php.net. But we prefer XAMPP because it also offers Apache and MySQL which are the most commonly used companions to PHP. Plus, it is really easy to install.
Apache Friends - XAMPP for Windows