This is not a question! I recently had been trying to get XAMPP as my local host to use different versions of PHP for testing. While it was not easy to get the information, I finally got it to work. I found all kinds of different instructions all over the net. Some use virtual servers and that is an option. This seemed to be the best for my needs. Some input from the Apache forum was critical to get this to work. I guess I was being annoying as they wanted me to go learn all about servers and server configurations! I am not a server guy and all I can show you is what I have working. PLEASE do not ask me to explain what is in the files. I have read through some of the documentation but I am still sort of lost. I am sure that there are some folks here on the forum that can explain this better. I am also trying to get Xdebug to work with all three versions as well. That is a work in progress. If you are interested, please keep reading.

First off, install the version of XAMPP you want to use as a base install. I have 7.4.25 as my installed base to xampp\

Next under you XAMPP create two new folders, in my case xampp/php8 (8.0.10 is the actual one) and xampp/php81v (8.1.1 is the actual version). Your base install version (7.4.25 for me) will be under xampp\php). Go to php.net and download the Windows version of that PHP file. Make sure you get the regular zip file as I cannot vouch for the others. I was told that the "debug" version was not the correct one. Unzip the PHP versions into the correct folder.

Under the XAMPP control panel, open httd-xampp.config file and add the following to the bottom of the file. Note how the versions are shown. you need to make four changes for each version as yours may be different. I went forward but I am told that you can go backwards to older versions if needed.

Code:
ScriptAlias /php8-cgi/ "C:/xampp/php8/"
<Directory "C:/xampp/php8">
    SetEnv PHPRC "C:/xampp/php8"
    AllowOverride None
    Options None
    Require all denied
    <Files "php-cgi.exe">
          Require all granted
    </Files>
</Directory>

ScriptAlias /php81-cgi/ "C:/xampp/php81/"
<Directory "C:/xampp/php81">
    SetEnv PHPRC "C:/xampp/php81"
    AllowOverride None
    Options None
    Require all denied
    <Files "php-cgi.exe">
          Require all granted
    </Files>
</Directory>
create a new .htaccess file for each version. The trick is to set the php version by using the .htaccess so you copy the correct .htaccess file to the store folder where you want to use the PHP version. I actually made two different files and named them PHP8htaccess and PHP81htaccess. All I have to do to change PHP versions is to rename either file to .htaccess.

for PHP 8.0.1, I used
Code:
<FilesMatch "\.php$">
    SetHandler application/x-httpd-php-cgi
</FilesMatch>

<IfModule actions_module>
    Action application/x-httpd-php-cgi "/php8-cgi/php-cgi.exe"
</IfModule>
and for 8.1.1, I used

Code:
<FilesMatch "\.php$">
    SetHandler application/x-httpd-php-cgi
</FilesMatch>

<IfModule actions_module>
    Action application/x-httpd-php-cgi "/php81-cgi/php-cgi.exe"
</IfModule>