在td元素内部回显时出错

我正在尝试查看一个数组是否为空，因此在<td>中我将写：不可用
我有这个PHP/PDO代码：

$sql1= "SELECT SUM(total_pay) AS total_w FROM workers WHERE date_of_pay = :d1 AND projects_id = :id";
    $stmt1 = $conn->prepare($sql1);
    $stmt1->bindValue(":d1", $d);
    $stmt1->bindValue(":id", $id);
    $count1 = $stmt1->execute();
    $result1 = $stmt1->fetchAll();
    $num1 = $stmt1->rowCount();

这是我的html代码：

<?php if($num1==0):?>
<td align="center">Not Available</td>
<?php else: ?>
<td align="center">
<?php 
{
    foreach ($result1 as $res1)
    {
        echo $res1['total_w'];
    }
}
?>
<?php endif; ?>
</td>

当数组不为空时，我有一个值，它将正常显示在<td>中，但当num1为空（$num1==0）时，即使Not Available 的文本也不会在<td>中显示

$result = $stmt1->fetch(PDO::FETCH_ASSOC);//SUM is only 1 row anyway
if ($result['total_w'] === null) {
    //no records found, no sum to display
} else {
    echo $result['total_w'];//show result
}