http://qaru.site/questions/60076/how-to-detect-search-engine-bots-with-php
if (preg_match('/bot|crawl|curl|dataprovider|search|get|spider|find|java|majesticsEO|google|yahoo|teoma|contaxe|yandex|libwww-perl|facebookexternalhit/i', $_SERVER['HTTP_USER_AGENT'])) {
// is bot
}
if (preg_match('/apple|baidu|bingbot|facebookexternalhit|googlebot|-google|ia_archiver|msnbot|naverbot|pingdom|seznambot|slurp|teoma|twitter|yandex|yeti/i', $_SERVER['HTTP_USER_AGENT'])) {