eZ\Publish\Core\REST\Common\Output\Generator\Xml\FieldTypeHashGenerator::generateNullValue PHP Метод

    protected function generateNullValue(\XmlWriter $writer, $key = null, $elementName = 'value')
    {
        $writer->startElement($elementName);
        $this->generateKeyAttribute($writer, $key);
        // @todo: xsi:type?
        $writer->endElement();
    }