»First-Click-Free Script - 1. Besucher & Google sieht Seite

<?php
// functions
function create_empty_file($filename) {
	$h = @fopen($filename, 'w');
	@flock($h, LOCK_EX);
	@fwrite($h, ' ');
	@flock($h, LOCK_UN);
	@fclose($h);
	@umask(0000);
	@chmod($filename, 0666);
}
function is_bot_agent() {
	if (
		strpos($_SERVER['HTTP_USER_AGENT'], 'bot') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'Bot') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'crawl') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'Crawl') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'search') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'get') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'spider') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'find') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'java') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'Java') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'Google') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'yahoo') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'ask') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'contaxe') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'Yandex') !== false ||
		strpos($_SERVER['HTTP_USER_AGENT'], 'libwww-perl') !== false
	) {
		return true;
	}
	return false;
}
function is_bot_host($host) {
	if (
		strpos($host, 'googlebot.com') !== false ||
		strpos($host, 'crawl.yahoo.net') !== false
	) {
		return true;
	}
	return false;
}
function is_se_user() {
	if (isset($_SERVER['HTTP_REFERER'])) {
		if (
			strpos($_SERVER['HTTP_REFERER'], '.google.') !== false ||
			strpos($_SERVER['HTTP_REFERER'], '.yahoo.') !== false
		) {
			return true;
		}
	}
	return false;
}
function is_bot() {
	if (is_bot_agent()) {
		if (!file_exists('cache/bots/' . crc32($_SERVER['REMOTE_ADDR']))) {
			if (is_bot_host(gethostbyaddr($_SERVER['REMOTE_ADDR']))) {
				create_empty_file(crc32($_SERVER['REMOTE_ADDR']));
				return true;
			}
		}
		else {
			return true;
		}
	}
	return false;
}
function is_view_allowed() {
	if (is_se_user()) {
		return true;
	}
	else if (is_bot()) {
		return true;
	}
	return false;
}
// check auth
if (!is_view_allowed()) {
	exit('Normaler Besucher ohne Google-Referer.');
}
?>