WordPress index.php seems to perform unwanted redirect 301

Question

Thanks in advance for any help provided.

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Configuration:

1. Debian Jessie
2. Front-end Nginx (1 server, 2 server_names; rewrites working correctly),
3. Proxied back-end Apache with no rewrites/aliases and other,
4. WordPress installed in /var/www/www.test.blog/wordpress/ with no plugins,
5. No constants declared in wp-config.php.

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Task:
I'm trying to make WP being resolved from multiple GET URLs:
test.blog and www.test.blog.

Due to Apache logs everything goes just fine until requesting reaches /var/www/www.test.blog/wordpress/index.php (line:18), after which, suddenly, appears response 301 to test.blog (line:19)

01:Request received from client: GET /wordpress/ HTTP/1.0
02:Headers received from client:
03:X-Real-IP: 10.0.2.2
04:X-Forwarded-For: 10.0.2.2
05:Host: www.test.blog
06:Connection: close
07:User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36
08:Upgrade-Insecure-Requests: 1
09:Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng
10:DNT: 1
11:Accept-Encoding: gzip, deflate
12:Accept-Language: ru-RU,ru;q=0.9,en-US;q=0.8,en;q=0.7
13:authorization result of Require all granted: granted
14:authorization result of <RequireAny>: granted
15:request authorized without authentication by access_checker_ex hook: /wordpress/
16:authorization result of Require all granted: granted
17:authorization result of <RequireAny>: granted
18:request authorized without authentication by access_checker_ex hook: /wordpress/index.php
19:Response sent with status 301, headers:
20:Date: Fri, 26 Jan 2018 14:20:49 GMT
21:Server: Apache/2.4.10 (Debian)
22:Location: http://test.blog/wordpress/
23:Content-Length: 0
24:Connection: close
25:Content-Type: text/html; charset=UTF-8

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Question:
Can it be that WP itself makes any redirect via PHP? I mean, it's totally capable of it, but does it happen actually _{(as I have no other suspects)}?
And if, what should I do to stop this behavior & finally make it being resolved from multiple URLs?

Answer 1

It sounds like both Home URL and Site URL for your blog are set to http://test.blog, while your server accepts both http://test.blog and http://www.test.blog.

If you access the latter, WordPress will redirect you because of the mismatch. You might be able to set the Home URL and Site URL dynamically in your wp-config.php like this:

define( 'WP_SITEURL', 'https://' . $_SERVER['HTTP_HOST'] );
define( 'WP_HOME',    'https://' . $_SERVER['HTTP_HOST'] );

This way, there shouldn't be a redirect. But this has of course complications for things like URLs in post content. WordPress does not use relative URLs for that. That's why it's generally better to settle one 1 domain. But there are also other reasons like SEO (duplicate content). Your web server should either redirect www.test.blog to test.blog or vice-versa, it's the easiest way to solve this. The site will obviously still be available via either host, it's just that you have to settle for one.

Note: $_SERVER['HTTP_HOST'] is not set on the command line, so if you want to use WP-CLI you'd have to set that variable.

Please let me know if that answers your question or if I misunderstood you.