Any way to fully replace nginx directives instead of appending

Hi
I'm trying to deploy a Symfony3 web site inside my local nginx server. Looking around I found that I need to write a vhost configuration like this:

Code:

server {
    server_name myserver.server.local www.myserver.server.local;
    root /var/www/clients/client1/web1/web/web;

    location / {
        # try to serve file directly, fallback to app.php
        try_files $uri /app.php$is_args$args;
    }
    # DEV
    # This rule should only be placed on your development environment
    # In production, don't include this and don't deploy app_dev.php or config.php
    location ~ ^/(app_dev|config)\.php(/|$) {
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
        # When you are using symlinks to link the document root to the
        # current version of your application, you should pass the real
        # application path instead of the path to the symlink to PHP
        # FPM.
        # Otherwise, PHP's OPcache may not properly detect changes to
        # your PHP files (see https://github.com/zendtech/ZendOptimizerPlus/issues/126
        # for more information).
        fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT $realpath_root;
    }
    # PROD
    location ~ ^/app\.php(/|$) {
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
       # When you are using symlinks to link the document root to the
       # current version of your application, you should pass the real
       # application path instead of the path to the symlink to PHP
       # FPM.
       # Otherwise, PHP's OPcache may not properly detect changes to
       # your PHP files (see https://github.com/zendtech/ZendOptimizerPlus/issues/126
       # for more information).
       fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
       fastcgi_param DOCUMENT_ROOT $realpath_root;
       # Prevents URIs that include the front controller. This will 404:
       # http://domain.tld/app.php/some-path
       # Remove the internal directive to allow URIs like this
       internal;
   }

   # return 404 for all other php files not matching the front controller
   # this prevents access to other php files you don't want to be accessible.
   location ~ \.php$ {
     return 404;
   }

   error_log /var/www/clients/client1/web1/web/var/logs/error.log;
   access_log /var/www/clients/client1/web1/web/var/logs/access.log;
}

but suddenly I figured out that writing this code inside the nginx directives section simply doesn't work because it doesn't override/overwrite the standard vhost configuration, but ispconfig appends it instead.

Could someone please tell me how could I do this without manually overwriting the vhost file? I'm new using ISPConfig3. Thank you