How To Make Blacklist And Skip blacklist String on PHP

    for ($i= 999; $i <= 99999; $i++){
        $cek = $i;
        $url = "http://rindsomxxxxxx.com/$cek";
        $headers = get_headers($url);
        $bom=explode(" ",$headers[0]);
        if ($bom[1] == 200) {
      $filess = "blacklist.txt";
      $handle = fopen($filess, 'a');
      fwrite($handle,  $cek);
      fwrite($handle, "\n");
      fclose($handle);
}}

Hello i Have PHP Code like that and i want to make some blacklist so when, $cek already found match number it will add to blacklist for next loop, how to add blacklist then? and how to make loop not from number 999 again when already meet blacklist number. ex: blacklist number 29912, and it will skip 29912 number to 29913.