Pimcore\Model\Document\PageSnippet::setContentMasterDocumentId PHP Method

    public function setContentMasterDocumentId($contentMasterDocumentId)
    {
        // this is that the path is automatically converted to ID => when setting directly from admin UI
        if (!is_numeric($contentMasterDocumentId) && !empty($contentMasterDocumentId)) {
            $contentMasterDocument = Document::getByPath($contentMasterDocumentId);
            if ($contentMasterDocument instanceof Document\PageSnippet) {
                $contentMasterDocumentId = $contentMasterDocument->getId();
            }
        }
        if (empty($contentMasterDocumentId)) {
            $contentMasterDocument = null;
        }
        if ($contentMasterDocumentId == $this->getId()) {
            throw new \Exception("You cannot use the current document as a master document, please choose a different one.");
        }
        $this->contentMasterDocumentId = $contentMasterDocumentId;
        return $this;
    }