how to identify web crawlers of google/yahoo/msn by PHP?

Question

AFAIK,

$_SERVER[\'REMOTE_HOST\'] should end up with \"google.com\" or \"yahoo.com\".

but is it the most ensuring method?

any other way out?

Answer 1

$_SERVER['HTTP_USER_AGENT']

• Google Bot = "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"
• MSN Bot = msnbot-products/1.0 (+http://search.msn.com/msnbot.htm)

Check various user agent strings here: http://www.user-agents.org/