/**
  * Adds a Global Alternative Experiment in the appropriate property.
  *
  * @param NelioABGlobalAlternativeExperiment $exp The Alternative Experiment to be added.
  * @param int $alt_index The index of the alternative that this visitor is supposed to see.
  *            If 0, the original version is added; if 1, the first
  *            alternative; if 2, the second; and so on.
  *
  * @since 4.0.0
  */
 private static function add_global_exp($exp, $alt_index)
 {
     $alt = $exp->get_original();
     if ($alt_index > 0) {
         --$alt_index;
         $alts = $exp->get_alternatives();
         if ($alt_index < count($alts)) {
             $alt = $alts[$alt_index];
         }
     }
     switch ($exp->get_type()) {
         case NelioABExperiment::CSS_ALT_EXP:
             self::$css_info = array('exp' => $exp, 'alt' => $alt);
             break;
         case NelioABExperiment::MENU_ALT_EXP:
             self::$menu_info = array('exp' => $exp, 'alt' => $alt);
             break;
         case NelioABExperiment::THEME_ALT_EXP:
             self::$theme_info = array('exp' => $exp, 'alt' => $alt);
             break;
         case NelioABExperiment::WIDGET_ALT_EXP:
             self::$widget_info = array('exp' => $exp, 'alt' => $alt);
             break;
     }
 }