install php8.1-fpm for multiversion PHP Debian

Here all the single element to install:

sudo apt-get install php8.1 php8.1-fpm php8.1-mysql libapache2-mod-php8.1 php8.1-curl php8.1-mbstring php8.1-xml php8.1-soap -y

then add the line number here:

fastcgi_pass unix:/run/php/php7.4-fpm.sock;