function addWarranty($name, $startTime, $warrantyPeriod, $description, $endTime) {
$mysqli = new mysqli(DATABASE_URL,DATABASE_LOGIN, DATABASE_PASSWORD, DATABASE_NAME);
	if($mysqli->connect_errno) {
		printf("Connect failed: %s\n", $mysqli->connect_error);
		exit();
	}
	if (!isUserLogged()) {
		return;
	}
	if (preg_match(PATTERN_NAME, $name) == 0) {
		return "error";
	}
	$date = date("Y-m-d");
	if ($endTime == "") {
		$endTime = date("Y-m-d", strtotime($startTime. '+' .$warrantyPeriod. 'days'));
	}
	else {
		$dateDiff = strtotime($endTime) - strtotime($startTime);
		$warrantyPeriod = floor($dateDiff/(86400));
	}
$query = "INSERT INTO tblwarranty (`name`, `StartTime`, `WarrantyPeriod`, `EndTime`, `description`, `u_id`, `DateAdded`) VALUES (?,?,?,?,?,?,?)";
	$stmt = $mysqli ->prepare($query);
$stmt->bind_param("ssissis", $name, $startTime, $warrantyPeriod, $endTime, $description, $_SESSION['id'], $date);
	$stmt->execute();
	$stmt->close();
	return "$name,$startTime,$endTime,$description,$mysqli->insert_id,$date";
}