private function extractFilenames(\ZipArchive $zipArchive)
    {
        $filenames = array();
        $fileCount = $zipArchive->numFiles;

        for ($i = 0; $i < $fileCount; $i++) {
            if (($filename = $this->extractFilename($zipArchive, $i)) !== false) {
                $filenames[] = $filename;
            }
        }

        return $filenames;
    }