framework/grid/CheckboxColumn.php
protected function renderHeaderCellContent()
    {
        if ($this->header !== null || !$this->multiple) {
            return parent::renderHeaderCellContent();
        }

        return Html::checkbox($this->getHeaderCheckBoxName(), false, ['class' => 'select-on-check-all']);
    }
protected function renderHeaderCellContent()
    {
        if ($this->header !== null || !$this->multiple) {
            return parent::renderHeaderCellContent();
        }

        return Html::checkbox($this->getHeaderCheckBoxName(), false, ['class' => 'select-on-check-all']);
    }
protected function renderHeaderCellContent ( ) { if ( $ this -> header !== null || ! $ this -> multiple ) { return parent :: renderHeaderCellContent ( ) ; } return Html :: checkbox ( $ this -> getHeaderCheckBoxName ( ) , false , [ 'class' => 'select-on-check-all' ] ) ; }
Renders the header cell content.
The default implementation simply renders [[header]].
This method may be overridden to customize the rendering of the header cell.
@return string the rendering result
Renders the header cell content . The default implementation simply renders [[ header ]] . This method may be overridden to customize the rendering of the header cell .