Very Life

<?php wp_head(); ?>

// get categories name
function get_cats_name() {
  $allcats=get_categories();
  foreach ($allcats as $category) 
  {
    $keywords[] = $category->cat_name;
  }
  return $keywords;
}
// utf8 substr
function utf8Substr($str, $from, $len) {
  return preg_replace('#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$from.'}'.
                      '((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$len.'}).*#s',
                      '$1',$str);
}
// Meta SEO
function meta_SEO() {
  global $post;
  $output = '';
  if (is_single()){//如果是文章页
    $keywords = ''; 
    $description = '';
    if ($post->post_excerpt) {//如果文章摘要存在就以文章摘要为描述
      $description = $post->post_excerpt;
      $description = str_replace("\r\n","",$description);
      $description = str_replace("\n","",$description);
      $description = str_replace("\"","'",$description);
      $description .= '...';
    } else {//如果文章摘要不存在就截断文章前200字为描述
      $description = utf8Substr(strip_tags($post->post_content),0,200);
      $description = str_replace("\r\n","",$description);
      $description = str_replace("\n","",$description);
      $description = str_replace("\"","'",$description);
      $description .= '...';
    }     
    $tags = wp_get_post_tags($post->ID);//取文章标签
    foreach ($tags as $tag ) {
      $keywordarray[] = $tag->name;
    }
    //以文章标签为关键字
    $keywords = implode(',',array_unique((array)$keywordarray));
  } else {//如果不是文章页
    $keywords = ''; //在引号间写入你博客的关键字用,断开
    $description = '';//在引号间写入你博客的简单描述，不要过200字
    if ($keywords == '') {//如果没写博客的关键字则以分类名为值
      $keywords = implode(',',array_unique((array)get_cats_name()));
    } 
    if ($description == '') {//如果没写博客的描述则以副标题为值
      $description = get_option('blogdescription');
    } 
  }
  //输出描述
  $output .= '<meta name="description" content="' . $description . '" />' . "\n";
  //输出关键字
  $output .= '<meta name="keywords" content="' . $keywords . '" />' . "\n";
  if (is_single() OR is_page() OR is_home()) ://如果是文章、分页、首页则允许robots
    $output .='<meta name="robots" content="index,follow,noarchive" />';
  else ://如果不是则不允许
    $output .='<meta name="robots" content="noindex,follow,noarchive" />';
  endif;
  $output .= "\n";
  $output .='<meta name="googlebot" content="noarchive" />';
  echo "$output\n";
}
add_action('wp_head', 'meta_SEO');//添加meta_SEO函数到头部信息里