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Detect crawlers/bots/spiders in PHP (simple and fast)
* Check if the given user agent string is one of a crawler, spider, or bot.
* @param string $user_agent
* A user agent string (e.g. Googlebot/2.1 (+
* @return bool
* TRUE if the user agent is a bot, FALSE if not.
function smart_ip_detect_crawler($user_agent) {
// User lowercase string for comparison.
$user_agent = strtolower($_SERVER['HTTP_USER_AGENT']);
// A list of some common words used only for bots and crawlers.
$bot_identifiers = array(
// See if one of the identifiers is in the UA string.
foreach ($bot_identifiers as $identifier) {
if (strpos($user_agent, $identifier) !== FALSE) {
return TRUE;
return FALSE;
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