code: protected function renderPageButton($label, $page, $class, $disabled, $active)
      {
          if ($active) {
              $class .= ' ' . $this->activePageCssClass;
          }
          if ($disabled) {
              $class .= ' ' . $this->disabledPageCssClass;
          }
          $state = $this->getState();
          $state['page'] = $page + 1;
          $jsonState = json_encode($state);
  
          $class .= ' stateful';
          $class = trim($class);
          $options = ['data-state' => $jsonState, 'class' => $class === '' ? null : $class];
  
          return Html::tag('li', Html::a($label, $this->pagination->createUrl($page), ['data-page' => $page]), $options);
      }
docs: Renders a page button.
  You may override this method to customize the generation of page buttons.
  
  @param string  $label    the text label for the button
  @param integer $page     the page number
  @param string  $class    the CSS class for the page button.
  @param boolean $disabled whether this page button is disabled
  @param boolean $active   whether this page button is active
  
  @return string the rendering result