Specifying multi-domain jails in Gollem FTP

Not exactly documented, most people may assume that setting an FTP jail is restricted to absolute paths in Gollem's backend.php.

This is clearly not suitable for servers where users log into virtual sites under different domains. Two styles of jails are then desired:

1. The user is restricted to /path/to/site-root/home/user
2. The user is restricted to /path/to/site-root (suitable for site owners)

Trouble is, the site-root location is a variable.

(section describing userhome-relative paths for root and home deleted)

(later...)

Turns out the problem was wrongly posed.

• FTP jail is normally handled by the FTP server in its configuration. proftp for example allows domain-specific jails. Fine.
• Problem is actually to dynamically set 'hostspec' to be the current user's domain so that one-click login to ftp works with correct ftp-server-resolving of appropriate jail root.

Is for example the current domain running horde available as
'hostspec' => $GLOBALS['something...'],

For that matter, is there any quick way to see what global values are available?

Possible solutions...

'hostspec' => $_SERVER['SERVER_NAME'],
which would howver need to be recast from e.g. 'webmail.example.com' to 'ftp.example.com'

And if ftp-login to explicit IP correctly references the appropriate virtual server configuration for jail path:
'hostspec' => $_SERVER['SERVER_ADDR'],

The last works in my setup at least.