During a migration from one IMAP server to another, the need arose to run both the old and the new IMAP servers in paralell. By default,

Horde only allows a single primary server to be enabled in servers.php. Of course, we could have allowed our users to simply select

their server by enabling IMAP server selection, but there is a better way. What follows are instructions on using a MySQL backend to

select an IMAP server for authentication, given a username:

+++ The SQL table

There are many ways to do this of course. In this example, we'll just be using a table with two rows:

Your table can be constructed however you like. It can even be a part of your existing Horde DB. The important point is that you need the

table to be constructed in such a way as to be able to query a username and have the lookup return a servername. Our example

uses a table called 'host'.

+++ Writing a hook

Here's some sample code for a hook placed inside horde/config/hooks.php:

    function _imp_hook_imap($userName)

    {

            global $conf;

            include_once 'DB.php';

            $_db = &DB::connect($conf['sql'], true);

            $query = sprintf('SELECT server FROM host WHERE user=%s', $_db->quote($userName));

            $result = $_db->getOne($query);

            if (!is_a($result, 'PEAR_Error')) {

                    return $result;

            } else {

                    return false;

            }

    }

+++ Placing the hook into the session

The above hook returns a single line containing a server name. It's injected into /horde/imp/lib/Session.php as follows:

    if (!empty($GLOBALS['conf']['hooks']['imap'])) {

            require_once HORDE_BASE . '/config/hooks.php';

            if (function_exists('_imp_hook_imap')) {

                    $_SESSION['imp']['server'] = call_user_func('_imp_hook_imap',  $_SESSION['imp']['user']);

                    }

    }

On our setup, this is done right before authentication is attempted (right around line 223). As best I can tell, you're fine so long

as you don't have $_SESSION['imp']['server'] overwritten by anything else before you get to the call to &Auth::singleton(array('imp', 'imp'));

+++ Disclaimer

This code works on our setup thus far. It could be wrong, uneccesary, foolish, or otherwise idiotic. In short, YMMV.

Questions? Send them to mp@xmission.com