不使用wordpress插件添加页面关键词和描述信息

<title><?php
if(is_category()){
single_cat_title();
}elseif(is_single() || is_page()){
single_post_title();
}elseif(is_search()){
echo wp_specialchars($s);
}else{
wp_title('',true);
}
if(! is_home()){
echo ' - ';
}
?></title>
<?php
if(is_page()){
$description = mb_strimwidth(strip_tags(apply_filters('the_content', $post->post_content)), 0, 200, '...');
$keywords = $post->post_title; 
}elseif(is_category()){
$description = trim(strip_tags(category_description($cat_ID)));
$keywords = single_cat_title('', false); 
}elseif(is_tag()){
$keywords = single_tag_title('', false); 
$description = trim(strip_tags(tag_description($tag_ID)));
}elseif(is_single()){
if($post->post_excerpt){
$description = $post->post_excerpt; 
}else{
$description = mb_strimwidth(strip_tags(apply_filters('the_content', $post->post_content)), 0, 200, '...'); 
}
$keywords = $post->post_title; 
}else{
$keywords = 'PHP博客,PHP,MySQL,Linux,C,编程算法,网站架构,互联网';
$description = '专注WEB开发,热爱PHP/MySQL/Linux/C/编程算法/网站架构,崇尚自由关注互联网';
}
?>
<meta name="keywords" content="<?php echo $keywords; ?>" />
<meta name="description" content="<?php echo str_replace(PHP_EOL, '', $description); ?>" />