// 正序
foreach($files as $file_num => $file) {
 if(is_file($directory.$file)){
  //$file = iconv("gb2312","UTF-8",$file); //或者 iconv("gb2312","UTF-8",$value);
  $date = substr($file,0,9);
  echo '<li class="world-cup-'.$date.'">';
  echo '<a href="'.$directory.$file.'" rel="worldcup" title="巴西世界杯赛事'.$date.'">';
  echo '<img src="'.$directory.$file.'" alt="">';
  echo '</a>';
  echo '</li>';
 }
}


// 倒序
foreach(array_reverse($files) as $file_num => $file) {
 if(is_file($directory.$file)){
  //$file = iconv("gb2312","UTF-8",$file); //或者 iconv("gb2312","UTF-8",$value);
  $date = substr($file,0,9);
  echo '<li class="world-cup-'.$date.'">';
  echo '<a href="'.$directory.$file.'" rel="worldcup" title="巴西世界杯赛事'.$date.'">';
  echo '<img src="'.$directory.$file.'" alt="">';
  echo '</a>';
  echo '</li>';
 }
}