src/Widgets/Bootstrap/Alert.php
protected function initOptions()
    {
        $this->htmlHlp->addCssClass($this->options, ['alert']);

        if ($this->closeButton !== false) {
            $this->htmlHlp->addCssClass($this->options, ['alert-dismissible', 'fade', 'show']);
            $this->closeButton = array_merge([
                'data-dismiss' => 'alert',
                'aria-hidden' => 'true',
                'aria-label' => 'Close',
                'class' => 'close',
            ], $this->closeButton);
        }
    }
protected function initOptions()
    {
        $this->htmlHlp->addCssClass($this->options, ['alert']);

        if ($this->closeButton !== false) {
            $this->htmlHlp->addCssClass($this->options, ['alert-dismissible', 'fade', 'show']);
            $this->closeButton = array_merge([
                'data-dismiss' => 'alert',
                'aria-hidden' => 'true',
                'aria-label' => 'Close',
                'class' => 'close',
            ], $this->closeButton);
        }
    }
Initializes the widget options.
This method sets the default values for various options.