function xxx_plz() {
  $plz_input = '/home/asp/albin/plz_tmp.txt';
  $plz_output = '/home/asp/albin/plz_freiburg.txt';
  $content = explode("\n", file_get_contents($plz_input));
  $plz_data = array();
  foreach ($content as $line) {
    list($plz, $rest) = 0;
    list($plz, $rest) = explode(' ', $line, 2);
    $plz_data[] = $plz;
  }
 
  sort($plz_data);
  $plz_data = array_unique($plz_data);
  $result = implode("\n", $plz_data);
  file_put_contents($plz_output, $result);
  $xx = 0;
 
}