/**
* Save a slider array in the database
* If ID is passed, it will update that ID.
* If no ID or ID = 0, it will insert
*
* @param $slider = array(); of slider data
* @return ID of saved slider or false if error
* @since 0.0.1
*/
protected function save_slider($slider)
{
// create a new object
$slider_obj = new Enp_quiz_Save_slider();
// pass to save_sliders so we can decide
// if we should insert or update the slider
$slider_obj->save_slider($slider);
}