function is_bot(){

    $bots = array(
        'Googlebot', 'Baiduspider', 'ia_archiver',
        'R6_FeedFetcher', 'NetcraftSurveyAgent', 'Sogou web spider',
        'bingbot', 'Yahoo! Slurp', 'facebookexternalhit', 'PrintfulBot',
        'msnbot', 'Twitterbot', 'UnwindFetchor',
        'urlresolver', 'Butterfly', 'TweetmemeBot' );

    foreach($bots as $b){
        if( stripos( $_SERVER['HTTP_USER_AGENT'], $b ) !== false ) return true;

    }
    return false;
}