Wrong wp-admin URL

Question

I freshly installed a WordPress site and I configured it behind a reverse proxy with site URL - http://example.com/hello

Problem

I can reach the admin dashboard page, however I cannot go further as the link becomes http://example.com/wp-admin instead of http://example.com/hello/wp-admin. How could I get rid of this weird behaviour?

Details that might help...

1. I am quite sure that the WordPress Address (URL) and Site Address (URL) are configured as http://example.com/hello, I even checked the database table wp_options.
2. When it arrives the admin dashboard page with correct CSS, the browser will show the correct link for half seconds and suddenly change to the wrong one. I even checked the network log in my Chrome and Firefox, the requested URL is http://example.com/hello/wp-admin.

3. I have tried to configure the .htaccess as well, but no luck.

   # BEGIN WordPress
   <IfModule mod_rewrite.c>
   RewriteEngine On
   RewriteBase /hello
   RewriteRule ^index\.php$ - [L]
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME} !-d
   RewriteRule . /hello/index.php [L]
   </IfModule>
   # END WordPress
   

Answer 1

Eventually, I found the reason of this weird behaviour.

It is caused by the JavaScript embedded in wp_admin_canonical_url() (https://developer.wordpress.org/reference/functions/wp_admin_canonical_url/)

The URL is determined by this piece of code

$_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']

where the latter one returns wp-admin instead of hello/wp-admin.

By manipulating the value in $_SERVER['REQUEST_URI'], I can successfully get the correct behaviour in admin dashboard. But I still hope for an elegant solution without touching WordPress code.

Answer 2

add_filter('set_url_scheme', 'hacky_uri_fix', 10, 2);
function hacky_uri_fix($url, $scheme) {
    if ( $url === {{BAD ADMIN URL}} ) {
        $url = {{CORRECT ADMIN URL}}
    }
    return $url
}

should work, just replace the bad URL you are trying to avoid with the correct one. I'm sure there's a better solution to this out there but I'm not super familiar with subfolder installs and this should work without touching core code.

Answer 3

Victor is 100%, so save the next person (maybe even myself) work digging further:

• the function wp_admin_canonical_url is in the ./wp-admin/includes/misc.php file

• Change

  $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']

to be

$_SERVER['HTTP_HOST'] . '/news/. $_SERVER['REQUEST_URI']

Where /news can be anything you have as a path in front of the wp-admin folder.