Nginx如何直接访问index.php时返回404

Question

For security purpose, I am attempting to hide almost all the fingerprint info of my web application. The most important thing is to hide PHP from any visitors. So I try to modify my Nginx's configuration file. The configuration will show as follows.

location / {
        root   /data/site/public;

        index  index.html index.htm index.php;
        try_files $uri /index.php;

        location /index.php {
            fastcgi_pass unix:/var/run/php5-fpm.sock;
            include fastcgi.conf;
        }
    }

By this way, I successfully hide index.php from URL. However, Hackers could also directly access my website by using some URL such as http://example.com/index.php, which shows that my website is written by PHP. Sometimes it maybe dangerous. So, I modify the Nginx's config second time, longing for 404 when access index.php directly, and it looks like

location / {
        root   /data/site/public;

        if ( $request_uri ~ /index\.php ) {
            return 404;
        }

        index  index.html index.htm index.php;
        try_files $uri /index.php;

        location /index.php {
            fastcgi_pass unix:/var/run/php5-fpm.sock;
            include fastcgi.conf;
        }
    }

However..., it seems that Nginx acts nothing different from the previous one.

Could anyone tell me the reason ? or any other solutions...