subdomain value in PHP (nginx) - php

Question

I have a Nginx webserver (I'm very new at Nginx). This is my Nginx config file:
server {
listen 80;
listen [::]:80;
server_name example.com *.example.com;
return 301 https://$server_name$request_uri;
}
server {
listen 443 ssl default_server;
listen [::]:443 ssl default_server;
ssl on;
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
ssl_session_timeout 5m;
root /var/www/html;
index index.php index.html index.htm index.nginx-debian.html;
server_name example.com *.example.com;
location / {
try_files $uri $uri/ =404;
}
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/run/php/php7.0-fpm.sock;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_TRANSLATED $document_root$fastcgi_script_name;
}
location ~ /\.ht {
deny all;
}
}
I have a DNS-record set to allow wildcard subdomains. My question now is: how can I "catch" the current subdomain in PHP?
For example: if the subdomain is http://demo.example.com, I want to go to
http://example.com?subdomain=demo.
Thanks in advance!

Answer 1

The host header will already contain the client requested domain. You could just grab that in php
$domain = $_SERVER['HTTP_HOST'];
However, unless you have a wildcard SSL certificate then you are going to have a bad time.
SSL negotiation takes place before any HTTP exchange so if the subdomain and the SSL cert don't agree the connection will fail.
Also, changing the subdomain to a query string is a bad idea:
You'll lose the ability to configure each subdomain separately within
Nginx and force lots of redirects and rewrites for every client
connection.
Your SEO will suck.
What will your page links look like?
If I have one.example.com and you have two.example.com the requests will become:
example.com?subdomain=one
example.com?subdomain=two
Both of those requests are now being handled by the same index page on example.com. Is that really what you want?

Answer 2

Add the following server to your Nginx. don't forget to restart Nginx service
server {
server_name demo.example.com;
rewrite ^(.*) http://example.com?subdomain=demo;
}
Update
according to the comment, for dynamic redirection, you should get the subdomain name by regex
server {
listen 80;
server_name ~^(?<name>.+)\.example\.com$;
return 301 http://example.com/?subdomain=$name;
}
Also, you can rewrite it instead of 301 redirects by
rewrite ^(.*) http://example.com/?subdomain=$name;
See this document for more info.