framework/grid/CheckboxColumn.php
protected function renderDataCellContent($model, $key, $index)
    {
        if ($this->content !== null) {
            return parent::renderDataCellContent($model, $key, $index);
        }

        if ($this->checkboxOptions instanceof Closure) {
            $options = call_user_func($this->checkboxOptions, $model, $key, $index, $this);
        } else {
            $options = $this->checkboxOptions;
        }

        if (!isset($options['value'])) {
            $options['value'] = is_array($key) ? Json::encode($key) : $key;
        }

        if ($this->cssClass !== null) {
            Html::addCssClass($options, $this->cssClass);
        }

        return Html::checkbox($this->name, !empty($options['checked']), $options);
    }
protected function renderDataCellContent($model, $key, $index)
    {
        if ($this->content !== null) {
            return parent::renderDataCellContent($model, $key, $index);
        }

        if ($this->checkboxOptions instanceof Closure) {
            $options = call_user_func($this->checkboxOptions, $model, $key, $index, $this);
        } else {
            $options = $this->checkboxOptions;
        }

        if (!isset($options['value'])) {
            $options['value'] = is_array($key) ? Json::encode($key) : $key;
        }

        if ($this->cssClass !== null) {
            Html::addCssClass($options, $this->cssClass);
        }

        return Html::checkbox($this->name, !empty($options['checked']), $options);
    }
{@inheritdoc}