实现代码：

// 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>";
	}
}