detect tablet

function is_tablet(){
	$tablet_browser = 0;
	$user_agent = $_SERVER['HTTP_USER_AGENT'];
	if (preg_match('/(tablet|ipad|playbook)|(android(?!.*(mobi|opera mini)))/i', strtolower($_SERVER['HTTP_USER_AGENT']))) {
		$tablet_browser++;
	}
	if ($tablet_browser > 0) {
		return true;
	} else {
		return false;
	}
}