Pimcore\Model\Object\ClassDefinition\Data\Multihref::getDataForResource PHP Method

    public function getDataForResource($data, $object = null, $params = [])
    {
        $return = [];
        if (is_array($data) && count($data) > 0) {
            $counter = 1;
            foreach ($data as $object) {
                if ($object instanceof Element\ElementInterface) {
                    $return[] = ["dest_id" => $object->getId(), "type" => Element\Service::getElementType($object), "fieldname" => $this->getName(), "index" => $counter];
                }
                $counter++;
            }
            return $return;
        } elseif (is_array($data) and count($data) === 0) {
            //give empty array if data was not null
            return [];
        } else {
            //return null if data was null  - this indicates data was not loaded
            return null;
        }
    }