Pimcore\Model\Document\Service::rewriteIds PHP Method

    public static function rewriteIds($document, $rewriteConfig, $params = [])
    {
        // rewriting elements only for snippets and pages
        if ($document instanceof Document\PageSnippet) {
            if (array_key_exists("enableInheritance", $params) && $params["enableInheritance"]) {
                $elements = $document->getElements();
                $changedElements = [];
                $contentMaster = $document->getContentMasterDocument();
                if ($contentMaster instanceof Document\PageSnippet) {
                    $contentMasterElements = $contentMaster->getElements();
                    foreach ($contentMasterElements as $contentMasterElement) {
                        if (method_exists($contentMasterElement, "rewriteIds")) {
                            $element = clone $contentMasterElement;
                            $element->rewriteIds($rewriteConfig);
                            if (Serialize::serialize($element) != Serialize::serialize($contentMasterElement)) {
                                $changedElements[] = $element;
                            }
                        }
                    }
                }
                if (count($changedElements) > 0) {
                    $elements = $changedElements;
                }
            } else {
                $elements = $document->getElements();
                foreach ($elements as &$element) {
                    if (method_exists($element, "rewriteIds")) {
                        $element->rewriteIds($rewriteConfig);
                    }
                }
            }
            $document->setElements($elements);
        } elseif ($document instanceof Document\Hardlink) {
            if (array_key_exists("document", $rewriteConfig) && $document->getSourceId() && array_key_exists((int) $document->getSourceId(), $rewriteConfig["document"])) {
                $document->setSourceId($rewriteConfig["document"][(int) $document->getSourceId()]);
            }
        } elseif ($document instanceof Document\Link) {
            if (array_key_exists("document", $rewriteConfig) && $document->getLinktype() == "internal" && $document->getInternalType() == "document" && array_key_exists((int) $document->getInternal(), $rewriteConfig["document"])) {
                $document->setInternal($rewriteConfig["document"][(int) $document->getInternal()]);
            }
        }
        // rewriting properties
        $properties = $document->getProperties();
        foreach ($properties as &$property) {
            $property->rewriteIds($rewriteConfig);
        }
        $document->setProperties($properties);
        return $document;
    }

 public function replaceAssignmentsAction()
 {
     $success = false;
     $message = "";
     $element = Element\Service::getElementById($this->getParam("type"), $this->getParam("id"));
     $sourceEl = Element\Service::getElementById($this->getParam("sourceType"), $this->getParam("sourceId"));
     $targetEl = Element\Service::getElementById($this->getParam("targetType"), $this->getParam("targetId"));
     if ($element && $sourceEl && $targetEl && $this->getParam("sourceType") == $this->getParam("targetType") && $sourceEl->getType() == $targetEl->getType()) {
         $rewriteConfig = [$this->getParam("sourceType") => [$sourceEl->getId() => $targetEl->getId()]];
         if ($element instanceof Document) {
             $element = Document\Service::rewriteIds($element, $rewriteConfig);
         } elseif ($element instanceof Object\AbstractObject) {
             $element = Object\Service::rewriteIds($element, $rewriteConfig);
         } elseif ($element instanceof Asset) {
             $element = Asset\Service::rewriteIds($element, $rewriteConfig);
         }
         $element->setUserModification($this->getUser()->getId());
         $element->save();
         $success = true;
     } else {
         $message = "source-type and target-type do not match";
     }
     $this->_helper->json(["success" => $success, "message" => $message]);
 }