//WordPress 文章关键词自动内链
function tag_sort($a, $b){
	if ( $a->name == $b->name ) return 0;
	return ( strlen($a->name) > strlen($b->name) ) ? -1 : 1;
}
function tag_link($content){
	$match_num_from = 1;	//一个标签少于几次不链接
	$match_num_to = 1;	//一个标签最多链接几次
	$posttags = get_the_tags();
	if ($posttags) {
		usort($posttags, "tag_sort");
		foreach($posttags as $tag) {
			$link = get_tag_link($tag->term_id);
			$keyword = $tag->name;
			//链接代码
			$cleankeyword = stripslashes($keyword);
			$url = "<a href=\"$link\" title=\"".str_replace('%s',addcslashes($cleankeyword, '$'),__('更多关于 %s 的文章'))."\"";
			$url .= ' target="_blank"';
			$url .= ">".addcslashes($cleankeyword, '$')."</a>";
			$limit = rand($match_num_from,$match_num_to);
			//不链接代码
			$content = preg_replace( '|(<a[^>]+>)(.*)<pre.*?>('.$ex_word.')(.*)<\/pre>(</a[^>]*>)|U'.$case, '$1$2%&&&&&%$4$5', $content);
			$content = preg_replace( '|(<img)(.*?)('.$ex_word.')(.*?)(>)|U'.$case, '$1$2%&&&&&%$4$5', $content);
			$cleankeyword = preg_quote($cleankeyword,'\'');
			$regEx = '\'(?!((<.*?)|(<a.*?)))('. $cleankeyword . ')(?!(([^<>]*?)>)|([^>]*?</a>))\'s' . $case;
			$content = preg_replace($regEx,$url,$content,$limit);
			$content = str_replace( '%&&&&&%', stripslashes($ex_word), $content);
		}
	}
	return $content;
}
add_filter('the_content','tag_link',1);

第二款

//自动TAG转内链
$match_num_from = 1; // 一个TAG标签出现几次才加链接
$match_num_to = 1; // 同一个标签加几次链接
add_filter('the_content','tag_link',1);
function tag_sort($a, $b){
if ( $a->name == $b->name ) return 0;
return ( strlen($a->name) > strlen($b->name) ) ? -1 : 1;
}
function tag_link($content){
global $match_num_from,$match_num_to;
$posttags = get_the_tags();
if ($posttags) {
usort($posttags, "tag_sort");
foreach($posttags as $tag) {
$link = get_tag_link($tag->term_id);
$keyword = $tag->name;
$cleankeyword = stripslashes($keyword);
$url = "<a href=\"$link\" title=\"".str_replace('%s',addcslashes($cleankeyword, '$'),__('View all posts in %s'))."\"";
$url .= ' target="_blank"';
$url .= ">".addcslashes($cleankeyword, '$')."</a>";
$limit = rand($match_num_from,$match_num_to);
$content = preg_replace( '|(<a[^>]+>)(.*)('.$ex_word.')(.*)(</a[^>]*>)|U'.$case, '$1$2%&&&&&%$4$5', $content);
$content = preg_replace( '|(<img)(.*?)('.$ex_word.')(.*?)(>)|U'.$case, '$1$2%&&&&&%$4$5', $content);
$cleankeyword = preg_quote($cleankeyword,'\'');
$regEx = '\'(?!((<.*?)|(<a.*?)))('. $cleankeyword . ')(?!(([^<>]*?)>)|([^>]*?</a>))\'s' . $case;
$content = preg_replace($regEx,$url,$content,$limit);
$content = str_replace( '%&&&&&%', stripslashes($ex_word), $content);
}
}
return $content;
}

把上面代码添加到functions.php文件后，当我们发布、更新、保存文章时，会自动检测文章中是否有标签关键词，如果有就会自动添加这些标签的链接。虽然是自动的，但我们还需注意以下两点：
1、上面代码中$match_num_to = 1; //一篇文章中同一个标签最多自动链接几次，这个建议最多只设置3次。
2、代码中的$posttags = get_tags();表示自动为文章添加全站所有标签链接，我们还可以改成只为此文章设置的标签添加链接，只需将“$posttags = get_tags();”改成“$posttags = get_the_tags();”即可。