1. Install PHP, Nginx and MySQL

Steps:

1. Install PHP by:

sudo aptitude install php7.0-fpm php7.0-cli php7.0-curl php7.0-gd php7.0-mcrypt php7.0-cgi php-mysql

2. Install Nginx by: sudo apt-get install nginx

Notice:

• if all module were installed sucessfully, you should be able to visit nginx root page by http://yourRaspberrypiIP
• Make sure all php packages were correctly installed, or the database may won't work at all.

2. Global configuration of Nginx and PHP

Steps:

1. Open configuration file by: sudo nano /etc/nginx/sites-available/default
2. Switch the location block with following passage

# old location block
location / {
                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
        }
# new location block		
location / {
		index  index.html index.htm index.php default.html default.htm default.php;
		}
		 
location ~\.php$ {
    fastcgi_pass unix:/run/php/php7.0-fpm.sock;
    #fastcgi_pass 127.0.0.1:9000;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    include fastcgi_params;
}

3. Insert index.php into server_name parameter as described in configuration file
4. Reload Nginx configuration and restart Nginx

sudo /etc/init.d/nginx reload
sudo service nginx restart

Notice:

• All web docs should be stored at /var/www/html
• So far your website can be visited by IP/correct path

3. Site specific configuration

This part configure the port, root and path of specific site.

Steps:

1. Create a new configuration file as following example and move it to /etc/nginx/sites-available/

server{
    listen 80;
    root /var/www/html;
    index index.php index.html index.htm index.nginx-debian.html;
    server_name example.com;

    location / {
        try_files $uri/ = 404;
    }
    location ~ \.php${
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix: /var/run/php/php7.0-fpm.sock;
    }
    location ~ /\.ht{
        deny all;
    }
}

2. Enable your new server block by creating a symbolic link from your new server block configuration file (in the /etc/nginx/sites-available/ directory) to the /etc/nginx/sites-enabled/ directory, unlink default configuration file. (From official guide)

sudo ln -s /etc/nginx/sites-available/example.com /etc/nginx/sites-enabled/
sudo unlink /etc/nginx/sites-enabled/default

3. Test and deploy configuration by:

sudo nginx -t  
sudo systemctl reload nginx

Notice:

• Each site should has its own configuration file in /etc/nginx/sites-enable, in this way it's easier to manage multiple site configurations in one web server.
• Refer to /var/log/nginx/error.log if any error occurs.