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>';
	}
}