smarty3 clearCache不起作用，返回值是0

[eightwhells]

代码片段
配置

$smarty = new Smarty();
$smarty->template_dir = getPath('tplPath');
$smarty->compile_dir = getPath('complierPath');
$smarty->cache_dir = getPath('cachePath');
$smarty->left_delimiter = '<{';
$smarty->right_delimiter = '}>';
$smarty->caching = true;
$smarty->addConfigDir(getPath('confPath'),'one');

清楚缓存段

//如果对应的帖子缓存已经存在，则销毁对应的缓存
        if($smarty->isCached('onePosts.html',"{$id}")){
           echo $result = $smarty->clearCache('onePosts.html',"{$id}");
             //echo $smarty->clearAllCache();      
        }