Php behind HTTPS/SSL Proxy (nginx, fastcgi)

nginx.conf

##
# nginx server with http + ssl/https (Front)
# /etc/nginx/sites-available/example.com
server {
  listen 80;
  server_name     example.com;

  location / {
    proxy_pass      http://no-ssl:8080;
    proxy_set_header  Host $host;
    proxy_set_header  X-Forwarded-Host $host;
    proxy_set_header  X-Real-IP $remote_addr;
    proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Proto $scheme;
  }
}

server {
  listen          443 ssl http2;
  server_name     example.com;
  ssl             on;
  #ssl_certificate /etc/<your_path>/fullchain.pem;
  #ssl_certificate_key /etc/<your_path>/privkey.pem;
  include snippets/ssl-params.conf;
      
  location / {
    proxy_pass        http://no-ssl:8080;
    proxy_set_header  Host $host;
    proxy_set_header  X-Forwarded-Host $host;
    proxy_set_header  X-Real-IP $remote_addr;
    proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Proto $scheme;
}
  
##
# server without ssl/https with fastcgi and Php runnning
# /etc/nginx/sites-available/example-behind-proxy.com
server {
  listen 8080 default_server;
  listen [::]:8080 default_server;
  server_name _;

  location / {
    try_files $uri $uri/ /index.php?$args;
  }

  location ~ \.php$ {
    include snippets/fastcgi-php.conf;
    set $my_https $https;
    if ($http_x_forwarded_proto = 'https') {
      set $my_https 'on';
    }

    fastcgi_param HTTPS $my_https; # set $_SERVER['HTTPS']
    fastcgi_param SERVER_NAME $host; # set $_SERVER['SERVER_NAME']
    fastcgi_param HTTP_HOST $host; # set $_SERVER['HTTP_HOST']
    fastcgi_pass unix:/run/php/php7.0-fpm.sock;
  }
}
  
# Next: Set the “Php Address (URL)” and “Site Address (URL)” to your new HTTPS address.
  
# See also:
# https://blog.virtualzone.de/2016/08/howto-https-ssl-wordpress-behind-proxy-nginx-haproxy-apache-lighttpd.html
# https://www.variantweb.net/blog/wordpress-behind-an-nginx-ssl-reverse-proxy/
# https://core.trac.wordpress.org/ticket/25239#no0