Why is the index.php downloaded instead of rendered by Nginx?

I have been banging my head for 2 days now. The issue is that the index.php is downloaded instead of being processed. I'm using Ubuntu 14.04 , Nginx, php5. The nginx/site-available/default is as below. I have added the index.php entry as prescribed by many posts.

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

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



    #server {
    #   listen 8000;
    #   listen somename:8080;
    #   server_name somename alias another.alias;
    #   root html;
    #   index index.php index.html index.htm;
    #
    #   location / {
    #       try_files $uri $uri/ =404;
    #   }
    #}


    # HTTPS server
    #
    #server {
    #   listen 443;
    #   server_name localhost;
    #
    #   root html;
    #   index index.php index.html index.htm;
    #
    #   ssl on;
    #   ssl_certificate cert.pem;
    #   ssl_certificate_key cert.key;
    #
    #   ssl_session_timeout 5m;
    #
    #   ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
    #   ssl_ciphers "HIGH:!aNULL:!MD5 or HIGH:!aNULL:!MD5:!3DES";
    #   ssl_prefer_server_ciphers on;
    #
    #   location / {
    #       try_files $uri $uri/ =404;
    #   }
    #}

The nginx.conf is as below..

user www-data;
worker_processes 4;
pid /run/nginx.pid;

events {
    worker_connections 768;
    # multi_accept on;
    }

http {

    ##
    # Basic Settings
    ##

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    # server_tokens off;

    # server_names_hash_bucket_size 64;
    # server_name_in_redirect off;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    ##
    # Logging Settings
    ##

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    ##
    # Gzip Settings
    ##

    gzip on;
    gzip_disable "msie6";

    # gzip_vary on;
    # gzip_proxied any;
    # gzip_comp_level 6;
    # gzip_buffers 16 8k;
    # gzip_http_version 1.1;
    # gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;

    ##
    # nginx-naxsi config
    ##
    # Uncomment it if you installed nginx-naxsi
    ##

    #include /etc/nginx/naxsi_core.rules;

    ##
    # nginx-passenger config
    ##
    # Uncomment it if you installed nginx-passenger
    ##

    #passenger_root /usr;
    #passenger_ruby /usr/bin/ruby;

    ##
    # Virtual Host Configs
    ##

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}


#mail {
#   # See sample authentication script at:
#   # http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript
# 
#   # auth_http localhost/auth.php;
#   # pop3_capabilities "TOP" "USER";
#   # imap_capabilities "IMAP4rev1" "UIDPLUS";
# 
#   server {
#       listen     localhost:110;
#       protocol   pop3;
#       proxy      on;
#   }
# 
#   server {
#       listen     localhost:143;
#       protocol   imap;
#       proxy      on;
#   }
#}

Solution followed till now.

1. added the entry of index.php
2. deleted the line default_type application/octet-stream; in nginx.conf
3. uncommented the fastcgi entries in default file.

I also tried these solution on the same problem but they didn't work for me.

• https://stackoverflow.com/questions/16747980/nginx-and-php-fpm-is-downloading-index-php-instead-of-processing-it
• one more link like it on stack overflow, along side many on other websites.

Sometimes it can be as simple as clearing the browser cache. If there was some misconfiguration and it was indeed downloading files, after fixing the config the browser needs to be told to stop using the cached download.

Make sure you installed php-fpm ,

sudo apt-get update && sudo apt-get install php5-fpm

now edit your nginx/site-available/default file and location ~ \.php$ block

 location ~ \.php$ {
                try_files $uri =404;
                fastcgi_split_path_info ^(.+\.php)(/.+)$;
                # 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;
        }

restart nginx service

sudo service nginx reload

and reload php5-fpm

sudo service php5-fpm restart