- strpos: documentation ( source)
- strtolower: documentation ( source)
<?php
$agenttotest = "Googlebot/2.1 (http://www.googlebot.com/bot.html)";
$agents_to_ignore = array("googlebot", "AdsBot", "pingdom", "bot");
foreach ($agents_to_ignore as $agent)
if (isset($agenttotest) && strpos(strtolower($agenttotest), strtolower($agent) !== false))
echo "block";