抛弃Auto Tags Link：不用插件实现关键词自动添加链接

这是比较老的一个技巧了，网上的资料显示文章内的关键词如果加上链接是有利于搜索引擎更好地收录的。比较著名的插件有Auto Tags Link，只为实现一个功能而动用插件太大材小用了，在functions.php中添加如下代码：

//连接数量
$match_num_from = 1; //一个关键字少于多少不替换
$match_num_to = 5; //一个关键字最多替换
//连接到WordPress的模块
add_filter('the_content','tag_link',1);
//按长度排序
function tag_sort($a, $b){
if ( $a->name == $b->name ) return 0;
return ( strlen($a->name) > strlen($b->name) ) ? -1 : 1;
}
//改变标签关键字
function tag_link($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;
//连接代码
$cleankeyword = stripslashes($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);
//不连接的代码
$content = preg_replace( '|(<a[^>]+>)(.*)('.$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;
}