First you must install and configure PHP-FPM. In Debian 12 there's PHP 8.2, but latest as of this writing is PHP 8.3.

sudo apt install apt-transport-https lsb-release ca-certificates
sudo wget -O /etc/apt/keyrings/php.gpg https://packages.sury.org/php/apt.gpg
echo "deb [signed-by=/etc/apt/keyrings/php.gpg] https://packages.sury.org/php/ $(lsb_release -sc) main" | \
sudo tee /etc/apt/sources.list.d/php.list
sudo apt update
sudo apt install php8.3 php8.3-{cli,fpm,curl,opcache,zip,intl,common,bcmath,xmlrpc,mbstring,xml,dom,mysqlnd,bz2,gd}

apt install lighttpd lighttpd-doc lighttpd-mod-deflate lighttpd-mod-gnutls \
lighttpd-mod-openssl spawn-fcgi

sudo mkdir -pv /home/sites/wiki/docroot