如何给z-blog设置关键字（keyword）和描述（description）

z-blog设置关键字（keyword）和描述（description）后，刚开始有，没有几天就消失了，我是在对应主题中的header.php这个文件增加的代码，想问下是什么原因造成的，该如何增明关键字和描述呢。谢谢！

if($type=='index'){
$keywords = $zbp->option['ZC_BLOG_SUBNAME'];
$description = $zbp->option['ZC_BLOG_COPYRIGHT'];
}elseif($type=='category'){
$keywords = $category->Name;
$description = $category->Intro;
}elseif($type=='article'||$type=='page'){
$aryTags = array();
foreach($article->Tags as $key){
$aryTags[] = $key->Name;
}
if(count($aryTags)>0) $keywords = implode(',',$aryTags);
$description = preg_replace('/[\r\n\s]+/', '', trim(SubStrUTF8(TransferHTML($article->Content,'[nohtml]'),100)).'...');
}{/php}{if isset($keywords)&&strlen($keywords)>0}<meta name="keywords" content="{$keywords}" />{/if}{if isset($description)&&strlen($description)>0}<meta name="description" content="{$description}" />{/if}