[ PHP ] block search engine bot

// block search engine bot
<?php
if(isset($_SERVER['HTTP_USER_AGENT']) && (preg_match('/bot|spider|crawler|slurp|teoma|archive|track|snoopy|java|lwp|wget|curl|client|python|libwww/i', $_SERVER['HTTP_USER_AGENT']))){
header("HTTP/1.0 404 Not Found");
header("Status: 404 Not Found");
die();
}
elseif(!isset($_SERVER['HTTP_USER_AGENT'])){
header("HTTP/1.0 404 Not Found");
header("Status: 404 Not Found");
die();
}
?>