original_string: public static function sortOrder($attribute = null)
      {
          if (!empty($attribute)) {
              $sort = Yii::$app->request->get('sort');
              if ($sort == $attribute) {
                  return ' ' . Html::tag('span', '', ['class' => 'glyphicon glyphicon-sort-by-alphabet']);
              }
              if ($sort == '-' . $attribute) {
                  return ' ' . Html::tag('span', '', ['class' => 'glyphicon glyphicon-sort-by-alphabet-alt']);
              }
          }
  
          return null;
      }
code: public static function sortOrder($attribute = null)
      {
          if (!empty($attribute)) {
              $sort = Yii::$app->request->get('sort');
              if ($sort == $attribute) {
                  return ' ' . Html::tag('span', '', ['class' => 'glyphicon glyphicon-sort-by-alphabet']);
              }
              if ($sort == '-' . $attribute) {
                  return ' ' . Html::tag('span', '', ['class' => 'glyphicon glyphicon-sort-by-alphabet-alt']);
              }
          }
  
          return null;
      }
code_tokens: public static function sortOrder ( $ attribute = null ) { if ( ! empty ( $ attribute ) ) { $ sort = Yii :: $ app -> request -> get ( 'sort' ) ; if ( $ sort == $ attribute ) { return ' ' . Html :: tag ( 'span' , '' , [ 'class' => 'glyphicon glyphicon-sort-by-alphabet' ] ) ; } if ( $ sort == '-' . $ attribute ) { return ' ' . Html :: tag ( 'span' , '' , [ 'class' => 'glyphicon glyphicon-sort-by-alphabet-alt' ] ) ; } } return null ; }
docstring: Returns sorting icon.
  @param string|null $attribute sorting attribute name
  @return string|null icon HTML or null if empty attribute
docstring_tokens: Returns sorting icon .