src/Factory/Form/AbstractCustomizableFieldsetFactory.php
protected function createFormInstance(ContainerInterface $container, $name, array $options = null)
    {
        if (!static::CLASS_NAME || !class_exists(static::CLASS_NAME)) {
            throw new \RuntimeException('The class constants "CLASS_NAME" must be non empty and name an existent class.');
        }

        $class = static::CLASS_NAME;

        return new $class(null, $options);
    }
protected function createFormInstance(ContainerInterface $container, $name, array $options = null)
    {
        if (!static::CLASS_NAME || !class_exists(static::CLASS_NAME)) {
            throw new \RuntimeException('The class constants "CLASS_NAME" must be non empty and name an existent class.');
        }

        $class = static::CLASS_NAME;

        return new $class(null, $options);
    }
Create the form/fieldset instance

@param ContainerInterface $container
@param string             $name
@param array              $options

@return \Zend\Form\Fieldset
@throws \RuntimeException