Sorry for the late reply. I'm curently at parental leave, thus my 
timeplanning is a bit unreliable ;)

Yes the hotfix works on my side, thanks!

As always great service!

Torben

Can you see if this commit fixes this behavior?

Changes have been made in Git (master):

commit c2470697f91dfc3cc04edbcab1e0e2ce84ded90a
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Sat Jan 14 12:44:38 2017 -0500

     Bug #14547 Fix using different protocols for the same driver type.

     When merging the base config for the SQL driver we must remove the
     inappropriate settings since they will both be present when the
     config arrays are merged.

  framework/Core/lib/Horde.php | 17 ++++++++++++++++-
  1 file changed, 16 insertions(+), 1 deletion(-)

http://github.com/horde/horde/commit/c2470697f91dfc3cc04edbcab1e0e2ce84ded90a

== Problematic behaviour ==
When using Horde with PHP7, it mixes pp the different SQL 
configurations in conf.php.
It is not possible to use a local PostgreSQL server as SQL default 
backend via unix socket, and a remote one for authentication via tcp. 
It always adds the socket value also to the auth backend and thus 
failes to connect.
It works as expected when using tcp for both servers.

Example (failing) conf.php:

$conf['sql']['username'] = 'horde-local';
$conf['sql']['password'] = 'LOCAL-PASSWORD';
$conf['sql']['socket'] = '/var/run/postgresql/';
$conf['sql']['protocol'] = 'unix';
$conf['sql']['database'] = 'horde';
$conf['sql']['charset'] = 'utf-8';
$conf['sql']['splitread'] = false;
$conf['sql']['phptype'] = 'pgsql';
$conf['nosql']['phptype'] = false;
$conf['ldap']['useldap'] = false;
$conf['auth']['admins'] = array( 'username@domain.tld', 'Administrator');
$conf['auth']['checkip'] = true;
$conf['auth']['checkbrowser'] = true;
$conf['auth']['resetpassword'] = false;
$conf['auth']['alternate_login'] = false;
$conf['auth']['redirect_on_logout'] = false;
$conf['auth']['list_users'] = 'input';
$conf['auth']['driver'] = 'sql';
$conf['auth']['params']['phptype'] = 'pgsql';
$conf['auth']['params']['username'] = 'horde-remote-for-auth';
$conf['auth']['params']['password'] = 'REMOTE-PASSWORD';
$conf['auth']['params']['hostspec'] = 'remote.host.tld';
$conf['auth']['params']['protocol'] = 'tcp';
$conf['auth']['params']['database'] = 'userdb';
$conf['auth']['params']['charset'] = 'utf-8';
$conf['auth']['params']['splitread'] = false;
$conf['auth']['params']['driverconfig'] = 'custom';
$conf['auth']['params']['table'] = 'users';
$conf['auth']['params']['username_field'] = 'email';
$conf['auth']['params']['password_field'] = 'password';
$conf['auth']['params']['encryption'] = 'crypt-sha512';
$conf['auth']['params']['show_encryption'] = false;
$conf['auth']['driver'] = 'sql';
$conf['auth']['params']['count_bad_logins'] = false;
$conf['auth']['params']['login_block'] = false;
$conf['auth']['params']['login_block_count'] = 5;
$conf['auth']['params']['login_block_time'] = 5;



Using instead
#$conf['sql']['socket'] = '/var/run/postgresql/';
#$conf['sql']['protocol'] = 'unix';
$conf['sql']['protocol'] = 'tcp';
#$conf['sql']['hostspec'] = 'localhost';

it works as expected.


horde is used with current stable releases installed via pear.

== Expected behaviour ==
Horde should seperate SQL and auth SQL fully, to be able to mix up SQL 
setups arbitrary.