[horde] Composite Authentication in Horde-3.1.1

[Manilal K M]

Hi all,
  I am setting up a horde installation with composite authentication
driver. Basically we have two set of users - One from the LDAP
database and the other from SQL database. In the case of SQL database
I am using the horde database and horde_users table. The configuration
is as follows:

$conf['auth']['params']['drivers']['corporate_sql']['driver'] = 'sql';
$conf['auth']['params']['drivers']['corporate_sql']['params'] = array(
    'driverconfig' => 'horde',
    'table' => 'horde_users',
    'username_field' => 'user_uid',
    'encryption' => 'md5-hex'
);

$conf['auth']['params']['drivers']['ldap']['driver'] = 'ldap';
$conf['auth']['params']['drivers']['ldap']['params'] = array(
    'hostspec' => 'localhost',
    'basedn' => 'c=US',
    'binddn' => 'cn=root,c=US',
    'password' => 'xxxxxxx',
    'version' => '3',
    'ad' => false,
    'uid' => 'uid',
    'encryption' => 'md5-hex',
    'newuser_objectclass' => array('shadowAccount', 'inetOrgPerson'),
    'objectclass' => array('top', 'person', 'qmailuser', 'CourierMailAccount'),
    'filter_type' => 'objectclass'
);

$conf['auth']['params']['admin_driver'] = 'ldap';
$conf['auth']['params']['loginscreen_switch'] = '_horde_select_loginscreen';
if (!function_exists('_horde_select_loginscreen')) {
    function _horde_select_loginscreen()
    {
        return 'ldap';
    }
}

I got the above configuration work successfully. Both these backends
have several set of users and all these users access horde with the
same URL.

My question is that, is it possible for the users to select the
authentication backend from the login screen ( from a drop-down box)
and then enter their credentials? If it's possible then how could I
configure it?

regards
-- 
Manilal K M.
മണിലാല് കെ. എം.