Adding rows to a HTML table with dynamic columns

I'm using the code below (provided as a solution to a previous question at Display mySQL records as HTML table columns) to generate an HTML table like:

Based on these tables:

The week names are in table 'week' and each week record also contains the number of sessions for that week:

+---------+-----------+----------+-----------+
| week_pk | week_name | sessions | cohort_fk |
+---------+-----------+----------+-----------+
|       1 | Week 1    |        3 |         1 |
|       2 | Week 2    |        2 |         1 |
|       3 | Week 3    |        1 |         1 |
+---------+-----------+----------+-----------+

+-----------+-------------+-------------+-------------+
| cohort_pk | cohort_name | cohort_code | cohort_year |
+-----------+-------------+-------------+-------------+
|         1 | Some name   | MICR8976    |        2014 |
+-----------+-------------+-------------+-------------+ 

I now want to extend this to show attendees as additional table rows under the session row and indicate which session they attended. The attendance table is:

+---------------+-------------+---------+-----------+---------+---------+
| attendance_pk | given_names | surname | cohort_fk | week_fk | session |
+---------------+-------------+---------+-----------+---------+---------+
|             1 | Bill        | Smith   |       1   |       2 |       2 |
|             2 | Fred        | Jones   |       1   |       1 |       1 |
+---------------+-------------+---------+-----------+---------+---------+

The resulting HTML table would be like:

Anyway help on modifying the code below to get results as per the above image appreciated.

$cohort = '1';
$year = '2014';

    $query = "SELECT * FROM cohort, week, attendance 
    WHERE week.cohort_fk = cohort.cohort_pk 
    AND attendance.week_fk = week.week_pk
    AND attendance.cohort_fk = cohort.cohort_pk
    AND cohort.cohort_year = '$year' 
    AND cohort.cohort_pk = '$cohort'";

    $result = mysql_query($query, $connection) or die(mysql_error());

    echo "<table border='1'>";
    echo "<tr><td>Name</td>";
    $second_row = "<tr><td>Session</td>";
    while($row = mysql_fetch_assoc($result)){
        $weekname  = $row["week_name"];
        $n_session = $row["sessions"];
        echo "<td colspan='$n_session'>$weekname</td>";
        for($i=1; $i<=$n_session; $i++){
            $second_row .= "<td>S$i</td>";
        }
    }
    echo "</tr>";
    echo "$second_row</tr>";
    echo "</table>";
    ?>