code: private function getFromZipArchive(ZipArchive $archive, $fileName = '')
      {
          // Root-relative paths
          if (strpos($fileName, '//') !== false) {
              $fileName = substr($fileName, strpos($fileName, '//') + 1);
          }
          $fileName = File::realpath($fileName);
  
          // Sadly, some 3rd party xlsx generators don't use consistent case for filenaming
          //    so we need to load case-insensitively from the zip file
  
          // Apache POI fixes
          $contents = $archive->getFromName($fileName, 0, ZipArchive::FL_NOCASE);
          if ($contents === false) {
              $contents = $archive->getFromName(substr($fileName, 1), 0, ZipArchive::FL_NOCASE);
          }
  
          return $contents;
      }
docs: @param ZipArchive $archive
  @param string $fileName
  
  @return string