Nginx config with maintenance support (PHP, CodeIgniter, Nginx)

production.conf

server {
    listen 80;
    server_name example.com;
    charset utf-8;
    rewrite_log on;
    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log notice;
    client_max_body_size 20M;

    root /usr/share/nginx/www/example.com/public;
    index index.html index.php;

    # Maintenance mode
    # ----------------
    # Create a file public/site_down to trigger a 503 response with a static
    # maintenance page.  User's from the local network will still be able to
    # get through though.

    set $maintenance 0;
    if (-f $document_root/site_down) {
        set $maintenance 1;
    }

    if ($remote_addr ~ "^(XXX.XXX.XXX.XXX)$") {
        set $maintenance 0;
    }

    if ($maintenance = 1) {
        return 503;
    }

    location / {
        try_files $uri $uri/ /index.php?$uri;
    }

    error_page 503 @maintenance_page;

    location @maintenance_page {
        rewrite ^(.*)$ /maintenance.html break;
    }

    location ~ \.php$ {
        include fastcgi_params;
        fastcgi_pass unix:/var/run/php5-fpm.sock;
      	fastcgi_index index.php;
        fastcgi_split_path_info ^(.+\.php)(.*)$;
	fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }

    location ~* \.(jpg|jpeg|png|gif|css|js|ico|svg)(\?[0-9]+)?$ {
        expires max;
    }
}