$zip = zip_open("zip.zip");
if (is_resource($zip)) {
  while ($zip_entry = zip_read($zip)) {
    $fp = fopen("zip/".zip_entry_name($zip_entry), "w");
    if (zip_entry_open($zip, $zip_entry, "r")) {
      $buf = zip_entry_read($zip_entry, zip_entry_filesize($zip_entry));
      fwrite($fp,"$buf");
      zip_entry_close($zip_entry);
      fclose($fp);
    }
  }
  zip_close($zip);
}