With nginx, all you have to do is use sockets via proxy_pass:

server{

    (...)

    location ~ ^/index.php(/|$) {

            fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;

            include fastcgi_params;

            fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;

            fastcgi_param DOCUMENT_ROOT $realpath_root;

    }

}

With apache you need to use proxy:

<FilesMatch ".php$">

     SetHandler "proxy:unix:/var/run/php/php7.2-fpm.sock|fcgi://localhost/"

</FilesMatch>

This way, you can use different sockets (each for different version of PHP) by configuring them within each Virtual Host