If you get a Fatal Error message, please look here.
If you get any other kind of Notice, Warning, Strict Standards, or Deprecated message please be advised that it is not a grave error and the extraction should be able to continue normally. If it doesn't, first ask your host how you can disable PHP error output to the browser or how you can set PHP's error reporting level to E_ERROR. We can't help you with that, as the process may be completely different on each host.