PHPePub\Core\EPub::saveBook PHP Method

    function saveBook($fileName, $baseDir = '.')
    {
        // Make fileName safe
        // $fileName = self::sanitizeFileName($fileName); // It is up to the user to ensure valid file names.
        // Finalize book, if it's not done already
        if (!$this->isFinalized) {
            $this->finalize();
        }
        if (!BinStringStatic::endsWith($fileName, ".epub")) {
            $fileName .= ".epub";
        }
        // Try to open file access
        $fh = fopen($baseDir . '/' . $fileName, "w");
        if ($fh) {
            fputs($fh, $this->getBook());
            fclose($fh);
            // if file is written return TRUE
            return $fileName;
        }
        // return FALSE by default
        return false;
    }

 /**
  * @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()));
 }