class Widget
{
    protected $title;
    protected $value
    protected $total;

    public function getType()
    {
        return 'widget';
    }
}

class BarWidget extends Widget
{
    public function getType()
    {
        return 'bar';
    }
}

class CircleWidget extends Widget
{
    protected $radius;
    protected $stroke;
    protected $duration;

    public function getType()
    {
        return 'circle';
    }
}

class WidgetRenderer
{
    public function render(array $widgets)
    {
        $output = [];

        foreach ($widgets as $widget) {
            $output[] = [
                'type' => $widget->getType(),
                'title' => $widget->getTitle(),
                ...
            ];
        }

        return $output;
    }
}

$bar = new Bar();
$bar->setTitle("Conversion rate {$repData->getKitActivationsAllTime()}/{$repData->getKitSetupsAllTime()}");
$bar->setValue($repData->getKitActivationsAllTime());

$circle = new Circle();
$circle->setTitle('Visits today');
$circle->setValue($repData->getVisitsCountToday());

$widgets = [
    $bar,
    $circle,
];

$renderer = new WidgetRenderer();
$renderer->render($widgets); // JSON