gistfile1.php

<?php

class BrokenDescrFilter extends FilterIterator {
  public function __construct(Iterator $iterator) {
    parent::__construct($iterator);
  }

  public function accept() {
    $file = $this->getInnerIterator()->current();
    if($file->getSize() == 18) {
      return true;
    }        
    return false;
  }
}

$di = new DirectoryIterator('downloads/pronox/descr/');
$di = new BrokenDescrFilter($di);

echo '<pre>';
$i = 1;
foreach($di as $file) {
  echo rtrim($file->getFileName(), '.xml') . ', ';
  if($i % 20 == 0) {
    echo "\n";
  }
  $i++;
}