Drupal in subdirectory behind reverse proxy

Question

On my public-facing host, Apache works as reverse proxy to a non-public host, where a Drupal 9 instance is symlinked under the web root. Drupal answers to requests, but it outputs any local links with the symlink name included. Apparently because the PHP request variable $_SERVER['SCRIPT_NAME'] includes it.

How do I tell Drupal about it's "actual" base path?

The details

Public host config:

<Location "/"> ProxyPreserveHost on ProxyPassReverse "https://otherserver/webb/" </Location> 

On otherserver, my domain example.com is a virtual host with its root in /var/www/sites/example.com/html. There is this symlink webb, pointing to the Drupal location:

/var/www/sites/example.com/html/webb -> /var/www/sites/example.com/html/drupal8/web/ 

Drupal responds, but in the response HTML, a link that should be to /about is instead to /webb/about, and the same goes for assets, etc.

If I echo $_SERVER['SCRIPT_NAME'], I get /webb/index.php.

Answer 1

I fixed this by altering REQUEST_URI and SCRIPT_NAME in settings.php:

$trim_path = '/webb'; if (isset($GLOBALS['request'])) { $request = $GLOBALS['request']; if ($request->server->get('SCRIPT_NAME') == "$trim_path/index.php") { $request->server->set('SCRIPT_NAME', '/index.php'); $request_uri = substr($request->server->get('REQUEST_URI'), strlen($trim_path)); $request->server->set('REQUEST_URI', $request_uri); } } 

Kudos to lightsurge for the earliest mention of this idea that I could find.