如何使用函数修改sql结果表示？

I am wondering if anyone can help? I am trying to output SQL in a table and I want to use functions 'slot' and 'groupnum' to modify the presentation of the output. When I try the code below the results are printing out in an unformatted way above the table rather than in it. Is there any fix for this?

  // Table header.
                        echo '<table>
                        <tr><td><b>Time Slot</b></td>
                        <td><b>Group</b></td>
                        </tr>';
                        // Fetch and display the records:
                        while ($row9 = mysqli_fetch_array($result9, MYSQLI_ASSOC)) {
                            echo '<tr>
                            <td>' .slot ($row9['slotid']). '</td>
                            <td>' .groupnum($row9['groupid']). '</td>
                            </tr>';
                        }
                        echo '</table>'; // Close the table.

Is this working?

echo '<table>'; // Open the table
while ($row9 = mysqli_fetch_array($result9, MYSQLI_ASSOC)) {
  echo '<tr>
          <td><code>' . slot($row9['slotid']) . '</code></td>
          <td><code>' .groupnum($row9['groupid']) . '</code></td>
        </tr>';
}
echo '</table>'; // Close the table.

You have missed the opening tag of the table element.

echo '<table>'; // Open the table.
while ($row9 = mysqli_fetch_array($result9, MYSQLI_ASSOC)) {
    echo '<tr>
    <td>' .slot ($row9['slotid']). '</td>
    <td>' .groupnum($row9['groupid']). '</td>
    </tr>';
}
echo '</table>'; // Close the table.

The problem was that I was using an echo statement in the function rather than return, so the code above is okay. The problem was with the functions.

//Right way
 function groupnum ($group){

    return "Group $group";
    }

//Wrong way
function groupnum ($group){

    echo "Group $group";
    }