PHP从tbl/fetch数组问题中选择

我的fetch_array有问题。我不断收到未找到的记录的返回。对于我所看到的每一件事，在我看来，这段代码应该可以工作。抱歉，我是php网页开发的新手。

$JobNumber = NULL;
if($_SERVER['REQUEST_METHOD'] == "POST")
{
$JobID = $_POST['jobid'];
include('pmconnect.php');
$sql="SELECT * FROM tblJobMaster WHERE JobNumber=" . $JobID;
$result=$conn->query($sql);
if ($result->num_rows==0)
    {
    echo "Record not found.<br>";
    die(0);
    }
$row=$result->fetch_array();
echo '<table style="text-align: left; width: 100%;" border="1" cellpadding="2" cellspacing="2">';
echo "<tbody>";
echo "<tr>";
echo '<td style="vertical-align: top; text-align: right;">Job Number:<br>';
echo "</td>";
echo '<td style="vertical-align: top;">' .$row[0] . '<br>';
echo "</td>";
echo '<td style="vertical-align: top; text-align: right;">Engineer:<br>';
echo '</td>';
echo '<td style="vertical-align: top;">' . $row[3] .'<br>';
echo '</td>';
echo "</tr>";
echo "<form action=pmAssignEngineer2.php method=post id=usrform>";
echo "<input type=hidden name=JobID value=" . $JobID . ">";
echo "<input type=submit value='"Update'" name=lookup>";
echo "</td>";
echo "</tr>";
echo "</form>";
echo "</tbody>";
}
else
{
echo "<form action=pmAssignEngineer.php method=post>";
echo "<table border=2>";
    echo "<tr>";
        echo "<td>Job Number:</td>";
        echo "<td><input type=text name=JobID></td>";
    echo "</tr>";
echo "</table>";
echo "<input type=submit value='"Lookup'" name=lookupQ><br>";
echo "</form>"; 
}