WordPress 自动为文章添加已使用过的标签

/** WordPress 自动为文章添加已使用过的标签 */
add_filter('the_content', 'auto_add_tags', 1 );
function auto_add_tags($content){
	$tags = get_tags( array('hide_empty' => false) );
	$limit = 1; // 设置同一个标签添加几次链接	
	$post_id = get_the_ID();
	if ($tags) {
		foreach ( $tags as $tag ) {
			// 如果文章内容出现了已使用过的标签，自动添加这些标签
			if ( strpos($content, $tag->name) !== false)
				wp_set_post_tags( $post_id, $tag->name, true );
 
			//替换文中出现的tag，替换次数需要设置limit
			$link = get_tag_link($tag->term_id);
			$keyword = $tag->name;
			if (preg_match_all('|(<h[^>]+>)(.*?)'.$keyword.'(.*?)(</h[^>]*>)|U', $content, $matchs)) {continue;}
			if (preg_match_all('|(<a[^>]+>)(.*?)'.$keyword.'(.*?)(</a[^>]*>)|U', $content, $matchs)) {continue;}
 
			$cleankeyword = stripslashes($keyword);
			$url = "<a href=\"$link\" title=\"".str_replace('%s',addcslashes($cleankeyword, '$'),__('查看与 %s 相关的文章', 'begin' ))."\"";
			$url .= ' target="_blank"';
			$url .= ">".addcslashes($cleankeyword, '$')."</a>";
			$cleankeyword = preg_quote($cleankeyword,'\'');
			$regEx = '\'(?!((<.*?)|(<a.*?)))('. $cleankeyword . ')(?!(([^<>]*?)>)|([^>]*?</a>))\'s' . $case;
			$content = preg_replace($regEx,$url,$content,$limit);
			$content = str_replace( '%&&&&&%', stripslashes($ex_word), $content);
 
		}
	}
	return $content;
}