src/Widgets/Bootstrap/Card.php
protected function renderFooter() {
        if (!isset($this->footer)) {
            return '';
        }
        if (isset($this->footerOptions)) {
            Html::addCssClass($this->footerOptions, ['widget' => 'card-footer']);
            $tag = ArrayHelper::remove($this->footerOptions, 'tag', 'div');
            $footer = $this->htmlHlp->tag($tag, $this->footer, $this->footerOptions);
        } else {
            $footer = $this->footer;
        }
        return $footer;
    }
protected function renderFooter() {
        if (!isset($this->footer)) {
            return '';
        }
        if (isset($this->footerOptions)) {
            Html::addCssClass($this->footerOptions, ['widget' => 'card-footer']);
            $tag = ArrayHelper::remove($this->footerOptions, 'tag', 'div');
            $footer = $this->htmlHlp->tag($tag, $this->footer, $this->footerOptions);
        } else {
            $footer = $this->footer;
        }
        return $footer;
    }
Render card footer
@return string