A special version of PHP for a specific IP address via NGINX

domain.test.conf

upstream php_fpm_9000 {
    server 127.0.0.1:9000;
}

upstream php_fpm_9001 {
    server 127.0.0.1:9001;
}

server {
    listen 80;
    server_name domain.test;

    root "/var/www/php/public";
    index index.html index.htm index.php;

    set $upstream_name 'php_fpm_9000';

    if ($remote_addr = 109.109.109.109) {
        set $upstream_name 'php_fpm_9001';
    }

    location ~ \.php$ {
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass $upstream_name;
        fastcgi_index index.php;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_intercept_errors off;
        fastcgi_buffer_size 16k;
        fastcgi_buffers 4 16k;
        fastcgi_connect_timeout 300;
        fastcgi_send_timeout 300;
        fastcgi_read_timeout 300;
    }
}