(PHP 5 >= 5.3.0, PHP 7)
Recorre un sistema de ficheros de forma similar a glob().
$pattern
   [, int $flags = FilesystemIterator::KEY_AS_PATHNAME | FilesystemIterator::CURRENT_AS_FILEINFO
  ] )$path
   [, int $flags = FilesystemIterator::KEY_AS_PATHNAME | FilesystemIterator::CURRENT_AS_FILEINFO | FilesystemIterator::SKIP_DOTS
  ] )