get configurable items of product magento 2

 $product_id = 25;

$objectManager = \Magento\Framework\App\ObjectManager::getInstance();

$configProduct = $objectManager->create('Magento\Catalog\Model\Product')->load($product_id);

foreach ($configProduct->getOptions() as $options)
{
    $optionData = $options->getValues();
    $parent_title = $options->getTitle();
    $parent_id = $options->getId();
    $parent[$parent_id] = $options->getTitle();
    foreach ($optionData as $data) {
        /* echo '<pre>';
         print_r($data->getData());
        echo '</pre>'; */
        $optionPrice [ $data['option_id'] ][ $data['title'] ] = $data->getPrice();
        $optionid [ $data['option_id'] ][ $data['title'] ] = $data['option_type_id'];
    }
}

$optionPricemyJSON = json_encode( $optionPrice );