[development] Loading configuration using 'SERVER_NAME' as opposed to 'HTTP_HOST'

[Adam Cooper]

> This is more a support question and should be on the support list  
> but see below.

Granted this is could be a support issue, but I had intended to  
(mostly) gauge the validity of a patch to core. Is that not a  
development question?

> My question back to you is why isn't HTTP_HOST properly setup?

AFAICT it is functioning exactly as designed. It returns the value of  
the Host: header as sent by the client. Numerous experiments with  
phpinfo() have confirmed that.

According to the apache docs (and confirmed by the above mentioned  
experiments) if UseCanonicalName is set to 'off' the SERVER_NAME  
variable is set to equal HTTP_HOST. This works great in most all  
cases. If UseCanonicalName is set to 'on' then SERVER_NAME is set to  
whatever 'ServerName' is set to in the apache conf. Seeing as  
UseCanonicalName can be set in the virtual host entry there is no  
problem doing something like this:

<VirtualHost *:80>
	UseCanonicalName On

	ServerName hostname.com
	ServerAlias hostname.dev
</VirtualHost>

If Drupal used the SERVER_NAME variable then accessing the site should  
load the hostname.com configuration regardless of what alias is  
accessed. Seeing as it uses HTTP_HOST it will fail to load a  
configuration.

> Generally, for Drupal multisites to work under different Apache
> configurations, Drupal needs to rely more on the client's HTTP request
> rather than the server configuration. You can see a related issue in
> http://drupal.org/node/262920

I suppose it's swings and roundabouts really. Using HTTP_HOST provides  
a globally predictable outcome. But if the user has access to the  
apache configuration, either by support request or personally, then  
SERVER_NAME provides a more configurable outcome.

I guess I'll just stick with symlinks (they can always be excluded  
from the version control anyway).

Thanks
Adam