Why are nginx+php-fpm scripts downloaded and not executed?

Question

PHP

I put on this link LEMP.
when testing a script, downloading is performed, and not working out.
the config itself:

server {
  listen 80 default_server;
  listen [::]:80 default_server;

        root /var/www/html;

  # Add index.php to the list if you are using PHP
  index index.php index.html index.htm index.nginx-debian.html;

  server_name 192.168.0.20;

  location / {
    # First attempt to serve request as file, then
    # as directory, then fall back to displaying a 404.
    try_files $uri $uri/ =404;
  }

  location ~ \.php$ {
    include snippets/fastcgi-php.conf;
  #
  #	# With php-fpm (or other unix sockets):
    fastcgi_pass unix:/var/run/php/php7.2-fpm.sock;
  #	# With php-cgi (or other tcp sockets):
  #	fastcgi_pass 127.0.0.1:9000;
  }
  location ~ /\.ht {
    deny all;
  }
}

Answer 1

Do your scripts start with <?or with <?php?
Well, look in /var/log/nginx/error.log