$_preserve : array
Any variables that should be preserved in all of the widget's links.
The Horde_Core_Ui_Pager:: provides links to individual pages.
Copyright 2004-2017 Horde LLC (http://www.horde.org/)
See the enclosed file LICENSE for license information (LGPL). If you did not receive this file, see http://www.horde.org/licenses/lgpl21.
preserve(string|array $var, mixed $value = null)
Instructs widget to preserve a variable or a set of variables.
The name of the variable to preserve, or an array of variables to preserve.
If preserving a single key, the value of the variable to preserve.