In order to update PHP 8.0.x to the latest 8.1.x version available, simply follow these steps:
Download and extract PHP 8.1 (8.1.x) VS16 x86 Thread Safe from this link: https://windows.php.net/download/
rename folder «php-8.1.x-Win32-vs16-x86\ext\» to «php-8.1.x-Win32-vs16-x86\extensions\»
copy «UniServerZ\core\php80\php_development.ini», «UniServerZ\core\php80\php_production.ini», «UniServerZ\core\php80\php_test.ini» and «UniServerZ\core\php80\php-cli.ini» to «php-8.1.x-Wi