$_POST variable empty on nginx

Hi, I just created a LEMP droplet with the default configuration. I’m using a PHP application that redirects all the requests to the main /index.php and this script takes care of all the routing and includes the correct files depending on the requested URI. I’ve been able to configure nginx to redirect all the request to that file:

location / {
                try_files $uri $uri/ /index.php?q=$uri&$args;
}

But it seems that when I POST a form to my website, the $_POST PHP variable is always empty. I did a search on Google, and found some answers on StackOverflow( like this and this), also tried to apply what I found on nginx’s documentation, but without any success.

My config file is now the following:

server {
        listen 80 default_server;
        listen [::]:80 default_server ipv6only=on;

        root /usr/share/nginx/html;
        index index.php index.html;

        ### Comment this once debug finished
        rewrite_log on;
        error_log /var/log/nginx/localhost.error_log notice;
        ### End

        # Make site accessible from http://localhost/
        (...)

        location / {
                try_files $uri $uri/ /index.php?q=$uri&$args;
        }

        error_page 404 /404.html;
        error_page 500 502 503 504 /50x.html;
        location = /50x.html {
                root /usr/share/nginx/html;
        }

        location ~ \.php$ {
                try_files = $uri @service;
                fastcgi_split_path_info ^(.+\.php)(/.+)$;
                fastcgi_pass unix:/var/run/php5-fpm.sock;
                fastcgi_index index.php;
                include fastcgi_params;
                fastcgi_param SCRIPT_FILENAME /usr/share/nginx/html$fastcgi_script_name;
                fastcgi_param QUERY_STRING q=$uri&$args;
                fastcgi_param REQUEST_METHOD $request_method;
                fastcgi_param CONTENT_TYPE $content_type;
                fastcgi_param CONTENT_LENGTH $content_length;
                fastcgi_param REQUEST_BODY $request_body;
        }

        location @service {
                fastcgi_param SCRIPT_FILENAME /usr/share/nginx/html/index.php;
                fastcgi_param SCRIPT_NAME     /index.php;
                fastcgi_param QUERY_STRING    q=$uri&$args;
        }

        (...)
}

Can anyone help me? Thanks in advance, Simone