简单写一下就行吧，蜘蛛名字随便写的不知道对不对：

$userAgent = $_SERVER['HTTP_USER_AGENT'];

$spiders = [
'Baiduspider', 'Sogou', 'Googlebot', 'Bingbot', 'YandexBot'
];

foreach ($spiders as $spider) {
if (stripos($userAgent, $spider) !== false) {
echo "访问者是：$spider";
break;
}
}