In nginx , the first file it will search for to open is the nginx index file.

In that case , in order to show your own index.php file, some configuration have to be made:

1. log in to root
2. vim /etc/nginx/sites-enabled/default
3. #Add index.php to the list if you are using PHP
   index index.html index.htm index.nginx-debian.html;
4. location ~ \.php$ {
   include snippets/fastcgi-php.conf;
   #
   # # With php5-cgi alone:
   # fastcgi_pass 127.0.0.1:9000;
   # # With php5-fpm:
   fastcgi_pass unix:/var/run/php5-fpm.sock;
   }
5. Remember to un command as step 4 because nginx itself cannot process php c

To trace the error log file :

tail -f /var/log/nginx/error.log