/**
  * 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);
 }