src/FormElements/Radio.php
public function getInputSpecification()
    {
        $haystack = \array_keys($this->getValueOptions());

        return [
            'name' => $this->getName(),
            'required' => $this->isRequired(),
            'validators' => [
                [
                    'name' => InArray::class,
                    'options' => ['haystack' => $haystack],
                ],
            ],
        ];
    }
public function getInputSpecification()
    {
        $haystack = \array_keys($this->getValueOptions());

        return [
            'name' => $this->getName(),
            'required' => $this->isRequired(),
            'validators' => [
                [
                    'name' => InArray::class,
                    'options' => ['haystack' => $haystack],
                ],
            ],
        ];
    }
Should return an array specification compatible with
{@link Zend\InputFilter\Factory::createInput()}.

@return array