Nginx – PHP-FPM with Nginx not Working on port 80

I am trying out nginx on my Ubuntu 14.04 desktop, I have referred to some basic setup articles and have installed the latest Nginx and PHP-FPM from the apt repository. I have nginx working and can get my html pages displayed on the browser, however when I try to call a .php page it downloads the .php file instead of rendering webpage with .php output. I am using the following server definition in the /etc/nginx/sites-available/default :

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

root /home/munjal/public_html;
index index.html index.htm;

# Make site accessible from http://localhost/
server_name localhost;

location / {
    # First attempt to serve request as file, then
    # as directory, then fall back to displaying a 404.
    # try_files $uri $uri/ =404;
    # Uncomment to enable naxsi on this location
    # include /etc/nginx/naxsi.rules
}

# Only for nginx-naxsi used with nginx-naxsi-ui : process denied requests
#location /RequestDenied {
#   proxy_pass http://127.0.0.1:8080;    
#}

#error_page 404 /404.html;

# redirect server error pages to the static page /50x.html
#
#error_page 500 502 503 504 /50x.html;
#location = /50x.html {
#   root /usr/share/nginx/html;
#}




# pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
#
location ~ \.php$ {
    fastcgi_split_path_info ^(.+\.php)(/.+)$;
#   # NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini
#
#   # With php5-cgi alone:
#   fastcgi_pass 127.0.0.1:9000;
#   # With php5-fpm:
    fastcgi_pass unix:/var/run/php5-fpm.sock;
    fastcgi_index index.php;
    include fastcgi_params;
}

# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
#location ~ /\.ht {
#   deny all;
#}

}

However now if I change my server definition to listen on port 8080 instead of 80 then the request is passed to php-fpm and a web page is rendered with the php output :

listen 8080 default_server;