php判断访问者是搜索引擎还是真实用户的代码

/**
 * 判断访问来源 搜索引擎还是真实用户
 * site bbs.it-home.org
*/
function is_bot()
{
 /* This function will check whether the visitor is a search engine robot */
 //根据需要扩充此数组
 $botlist = array("Teoma", "alexa", "froogle", "Gigabot", "inktomi",
 "looksmart", "URL_Spider_SQL", "Firefly", "NationalDirectory",
 "Ask Jeeves", "TECNOSEEK", "InfoSeek", "WebFindBot", "girafabot",
 "crawler", "bbs.it-home.org", "Googlebot", "Scooter", "Slurp",
 "msnbot", "appie", "FAST", "WebBug", "Spade", "ZyBorg", "rabaz",
 "Baiduspider", "Feedfetcher-Google", "TechnoratiSnoop", "Rankivabot",
 "Mediapartners-Google", "Sogou web spider", "WebAlta Crawler","TweetmemeBot",
 "Butterfly","Twitturls","Me.dium","Twiceler");

 foreach($botlist as $bot)
 {
     if(strpos($_SERVER['HTTP_USER_AGENT'],$bot)!==false)
     return true;    // Is a bot
 }

 return false;   // Not a bot
}
?>