我对编程还不熟悉，正努力让时间表工作。我的问题是，无论我尝试什么，我都无法让我的php检查我的db on endwork中的值是set还是null(截至目前为空）

<?php
if (isset($_POST['setTimestamp'])) {
$date = $_POST['date'];
$workDate = date('Y-m-d');

$dateQuery = "SELECT WorkDate FROM WorkingHours WHERE WorkDate = 
'$workDate'";
$eWorkQuery = "SELECT EndWork FROM WorkingHours WHERE WorkDate = 
'$workDate'";
$eBreakQuery = "SELECT EndBreak FROM WorkingHours WHERE WorkDate = 
'$workDate'";
$sBreakQuery = "SELECT StartBreak FROM WorkingHours WHERE WorkDate = 
'$workDate'";
$sWorkQuery = "SELECT StartWork FROM WorkingHours WHERE WorkDate = 
'$workDate'";

$d_query_run = mysqli_query($con, $dateQuery);
$e_w_query_run = mysqli_query($con, $eWorkQuery);
$e_b_query_run = mysqli_query($con, $eBreakQuery);
$s_b_query_run = mysqli_query($con, $sBreakQuery);
$s_w_query_run = mysqli_query($con, $sWorkQuery);

if (mysqli_num_rows($d_query_run)==1) {

    if (!isset($e_w_query_run)) {

        if (empty($e_b_query_run)) {

            if (empty($s_b_query_run)) {

                if (empty($s_w_query_run)) {
                }
                else{
                    echo " set StartBreak's time to localtime ";
                }

            }
            else{
                echo " set EndBreak's time to localtime ";
            }

        }
        else{
            echo " set EndWork's time to localtime ";
        }

    }

    else{
        echo " You already submited your timesheet for today ";
        echo "<pre>" ,print_r($e_w_query_run, TRUE),"</pre>";
    }

}
else{
    echo " set StartWork's time to localtime";
}

}
?>

下面的代码行仅用于检查查询的输出。

echo "<pre>" ,print_r($e_w_query_run, TRUE),"</pre>";

我试过了 !isset() is_null empty() . 它告诉我，它不能在对象上使用这些操作，而是在数组上使用这些操作。正因为如此，我试了一下 mysqli_fetch_array 但这也不管用。
如果有人能帮我解决这个问题，那就太棒了，还要提前感谢。