function is_spider(){
$robot = 0;
$USER_AGENT = strtolower($_SERVER['HTTP_USER_AGENT']);
if(strpos($USER_AGENT,"bot")) $robot = 1;
if(strpos($USER_AGENT,"spider")) $robot = 1;
if(strpos($USER_AGENT,"slurp")) $robot = 1;
if(strpos($USER_AGENT,"mediapartners-google")) $robot = 1;
if(strpos($USER_AGENT,"fast-webcrawler")) $robot = 1;
if(strpos($USER_AGENT,"altavista")) $robot = 1;
if(strpos($USER_AGENT,"ia_archiver")) $robot = 1;
if($robot == 1){
//do something
}
return '';
}

function isCrawler() {
    echo $agent= strtolower($_SERVER['HTTP_USER_AGENT']);
    if (!empty($agent)) {
        $spiderSite= array(
            "TencentTraveler",
            "Baiduspider+",
            "BaiduGame",
            "Googlebot",
            "msnbot",
            "Sosospider+",
            "Sogou web spider",
            "ia_archiver",
            "Yahoo! Slurp",
            "YoudaoBot",
            "Yahoo Slurp",
            "MSNBot",
            "Java (Often spam bot)",
            "BaiDuSpider",
            "Voila",
            "Yandex bot",
            "BSpider",
            "twiceler",
            "Sogou Spider",
            "Speedy Spider",
            "Google AdSense",
            "Heritrix",
            "Python-urllib",
            "Alexa (IA Archiver)",
            "Ask",
            "Exabot",
            "Custo",
            "OutfoxBot/YodaoBot",
            "yacy",
            "SurveyBot",
            "legs",
            "lwp-trivial",
            "Nutch",
            "StackRambler",
            "The web archive (IA Archiver)",
            "Perl tool",
            "MJ12bot",
            "Netcraft",
            "MSIECrawler",
            "WGet tools",
            "larbin",
            "Fish search",
        );
        foreach($spiderSite as $val) {
            $str = strtolower($val);
            if (strpos($agent, $str) !== false) {
                return true;
            }
        }
    } else {
        return false;
    }
}
if (isCrawler()){
    echo "你好蜘蛛精！";
}
else{
   echo "你不是蜘蛛精啊！";
}