php代码禁止搜索引擎蜘蛛

其实robots.txt也不是百分之百的可以阻止蜘蛛爬行你的网站，我自己结合某些资料写了一小段代码，貌似可以彻底解决这个问题，不对的地方请大家多多指教：

if(preg_match("/(Googlebot|Msnbot|YodaoBot|Sosospider|baiduspider|google|baidu|yahoo|sogou|bing|coodir|soso|youdao|zhongsou|slurp|ia_archiver|scooter|spider|webcrawler|OutfoxBot)/i", $_SERVER['HTTP_USER_AGENT'])){
header('HTTP/1.1 403 Forbidden');
exit;
}

<?php
wp_head();
if(preg_match("/(Msnbot|YodaoBot|Sosospider|baiduspider|baidu|sogou|bing|coodir|soso|youdao|zhongsou|slurp|ia_archiver|scooter|spider|webcrawler|OutfoxBot)/i", $_SERVER['HTTP_USER_AGENT'])){
header('HTTP/1.1 403 Forbidden');
exit;
}
?>

<?php if(in_category('指定分类ID')) {?>代码<?php }?> 禁止蜘蛛爬行指定的分类