PHP-foreach循环中的Select语句

Question

正在尝试运行以下代码：

foreach ($tags as $tag)
{   
    $tag = strtolower($tag);
    $tag = trim($tag);
    echo "<br>" . $tag . " checking<br>";

    $query = "SELECT `tag_id`, `tag_name` FROM TAG where `tag_name` = ?";
    $stmt = mysqli_prepare($connection, $query);
    $stmt->bind_param("s", $tag);

    if ($stmt->execute())
    {
        echo "Success";
    }
    else
    {
        echo "Error";
    }
}

我的$tags数组有food, school, Birthday, not, There, over, Limit。

前三个元素food, school, Birthday在我的TAG表中

我得到的输出是

food checking
Success
school checking

然后页面崩溃，出现500错误，并且无法继续加载。对于可能破坏这里的代码感到很困惑。