PHPePub\Core\EPub::finalize PHP Method

    function finalize()
    {
        if ($this->isFinalized || $this->chapterCount == 0 || empty($this->title) || empty($this->language)) {
            return false;
        }
        if (empty($this->identifier) || empty($this->identifierType)) {
            $this->setIdentifier(StringHelper::createUUID(4), EPub::IDENTIFIER_UUID);
        }
        if ($this->date == 0) {
            $this->date = time();
        }
        if (empty($this->sourceURL)) {
            $this->sourceURL = URLHelper::getCurrentPageURL();
        }
        if (empty($this->publisherURL)) {
            $this->sourceURL = URLHelper::getCurrentServerURL();
        }
        // Generate OPF data:
        $this->opf->setIdent("BookId");
        $this->opf->initialize($this->title, $this->language, $this->identifier, $this->identifierType);
        $DCdate = new DublinCore(DublinCore::DATE, gmdate($this->dateformat, $this->date));
        $DCdate->addOpfAttr("event", "publication");
        $this->opf->metadata->addDublinCore($DCdate);
        if (!empty($this->description)) {
            $this->opf->addDCMeta(DublinCore::DESCRIPTION, StringHelper::decodeHtmlEntities($this->description));
        }
        if (!empty($this->publisherName)) {
            $this->opf->addDCMeta(DublinCore::PUBLISHER, StringHelper::decodeHtmlEntities($this->publisherName));
        }
        if (!empty($this->publisherURL)) {
            $this->opf->addDCMeta(DublinCore::RELATION, StringHelper::decodeHtmlEntities($this->publisherURL));
        }
        if (!empty($this->author)) {
            $author = StringHelper::decodeHtmlEntities($this->author);
            $this->opf->addCreator($author, StringHelper::decodeHtmlEntities($this->authorSortKey), MarcCode::AUTHOR);
            $this->ncx->setDocAuthor($author);
        }
        if (!empty($this->rights)) {
            $this->opf->addDCMeta(DublinCore::RIGHTS, StringHelper::decodeHtmlEntities($this->rights));
        }
        if (!empty($this->coverage)) {
            $this->opf->addDCMeta(DublinCore::COVERAGE, StringHelper::decodeHtmlEntities($this->coverage));
        }
        if (!empty($this->sourceURL)) {
            $this->opf->addDCMeta(DublinCore::SOURCE, $this->sourceURL);
        }
        if (!empty($this->relation)) {
            $this->opf->addDCMeta(DublinCore::RELATION, StringHelper::decodeHtmlEntities($this->relation));
        }
        if ($this->isCoverImageSet) {
            $this->opf->addMeta("cover", "CoverImage");
        }
        if (!empty($this->generator)) {
            $gen = StringHelper::decodeHtmlEntities($this->generator);
            $this->opf->addMeta("generator", $gen);
            $this->ncx->addMetaEntry("dtb:generator", $gen);
        }
        if ($this->EPubMark) {
            $this->opf->addMeta("generator", "EPub (Version " . self::VERSION . ") by A. Grandt, http://www.phpclasses.org/package/6115 or https://github.com/Grandt/PHPePub/");
        }
        reset($this->ncx->chapterList);
        list($firstChapterName, $firstChapterNavPoint) = each($this->ncx->chapterList);
        /** @var $firstChapterNavPoint NavPoint */
        $firstChapterFileName = $firstChapterNavPoint->getContentSrc();
        $this->opf->addReference(Reference::TEXT, StringHelper::decodeHtmlEntities($firstChapterName), $firstChapterFileName);
        $this->ncx->setUid($this->identifier);
        $this->ncx->setDocTitle(StringHelper::decodeHtmlEntities($this->title));
        $this->ncx->referencesOrder = $this->referencesOrder;
        if ($this->isReferencesAddedToToc) {
            $this->ncx->finalizeReferences();
        }
        $this->finalizeTOC();
        if (!$this->isEPubVersion2()) {
            $this->addEPub3TOC("epub3toc.xhtml", $this->buildEPub3TOC());
        }
        $opfFinal = StringHelper::fixEncoding($this->opf->finalize());
        $ncxFinal = StringHelper::fixEncoding($this->ncx->finalize());
        if (mb_detect_encoding($opfFinal, 'UTF-8', true) === "UTF-8") {
            $this->zip->addFile($opfFinal, $this->bookRoot . "book.opf");
        } else {
            $this->zip->addFile(mb_convert_encoding($opfFinal, "UTF-8"), $this->bookRoot . "book.opf");
        }
        if (mb_detect_encoding($ncxFinal, 'UTF-8', true) === "UTF-8") {
            $this->zip->addFile($ncxFinal, $this->bookRoot . "book.ncx");
        } else {
            $this->zip->addFile(mb_convert_encoding($ncxFinal, "UTF-8"), $this->bookRoot . "book.ncx");
        }
        $this->opf = null;
        $this->ncx = null;
        $this->isFinalized = true;
        return true;
    }

 /**
  * @param null|string $filename
  * @return void
  */
 public function save($filename = null)
 {
     if (is_null($filename)) {
         $filename = time() . Random::getRandStr(32);
     }
     $this->filename = $filename;
     $this->epub->finalize();
     $this->epub->saveBook($filename, storage_path($this->getPath()));
 }