Many thanks for this answer danliker.
Unfortunately Horde still to show a blank page on redirect.php also with php_admin_flag error_reporting "E_ERROR & E_CORE_ERROR & E_USER_ERROR & E_COMPILE_ERROR".
In Apache logs I found also this error :
Hi IgorG I've a similar issue with Horde.At login a blank page is shown and I must reload page for displaying items.Also logs look like this :
Any suggestion?Thanks.