我的Google的aggregateRating无效。谷歌页面https://developers.google.com/structured-data/在此行中显示错误：
<span itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating">
错误：无法标准化评级值
谁可以提供帮助？
<!-- Start ShopVote.de-Rating-Snippet -->
<?php $xml_rating ="https://www.shopvote.de/betreiber/get_rating.php?rateid=e218b-5650-ec2c8";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $xml_rating);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$output = curl_exec($ch);
curl_close($ch);
if ($xml = simplexml_load_string($output)) { ?>
<span itemscope itemtype="http://schema.org/WebPage">
<span>ShopVote-Note von <span itemprop="name"><? echo $xml->data->shopdomain; ?></span>: </span>
<meta itemprop="url" content="<? echo $xml->data->shopurl; ?>">
<span itemprop="aggregateRating" itemscope itemtype="http://schema.org/AggregateRating">
<? echo $xml->data->rating; ?> (entspricht <span itemprop="ratingValue"><? echo $xml->data->stars; ?></span> / 5 Sternen) aus
<span itemprop="ratingCount"><? echo $xml->data->counter; ?></span>
<a itemprop="sameAs" href="https://www.shopvote.de/bewertung_richtiggutbewerben_de_5650.html" target="_blank">Bewertungen</a>
</span></span><?php } ?>
<!-- ENDE ShopVote.de-Rating-Snippet-->
万分感谢。
