nested while loops php mysql - php

Question

I have this code:
<?php
if( isset($_POST['groups'])){
$groups = $_POST['groups'];
$subject = $_POST['subject'];
$sql="SELECT
a.groupcode, a.groupstudents, a.studentid,
b.groupcode, b.coursename, b.studentid, b.date, b.class1, b.attend, b.attendno
FROM table_1 a, table_2 b
WHERE b.groupcode = '$groups' AND b.coursename = '$subject' AND
(a.studentid = b.studentid AND a.groupcode = b.groupcode)";
$result=mysqli_query($GLOBALS["___mysqli_ston"], $sql); ?>
<table width="100%" border="1" cellspacing="0" cellpadding="3" >
<tr>
<td align="center"><strong><font size="2">Students</font></strong></td>
<td align="center"><strong><font size="2">Date</font></strong></td>
<td align="center"><strong><font size="2">Attendance</font></strong> </td>
</tr>
<?php
while($rows=mysqli_fetch_array($result)){
$date = $rows['date']; $date2 = date("d-F-Y", strtotime($date));
$class1 = $rows['class1'];
if ($class1 == 0) $class1 = "No Class"; if ($class1 == 1) $class1 = "Absent";
if ($class1 == 3) $class1 = "Present"; if ($class1 == 2) $class1 = "Late";
?>
<tr>
<td align="center"><font size="2"><?php echo $rows['groupstudents']; ?></font> </td>
<td align="center"><strong><font size="2"><?php echo $date2; ?></font></strong> </td>
<td align="center"><font size="2"><?php echo $class1; ?></font></td>
</tr>
<?php
}
?>
which gives the below output.
Now my question is how to modify my code (use nested loops?!) so the output is:
Thank you kindly.
NB: Sorry, I do not have enough reputation to attach images. I have uploaded them on an external site.

Answer 1

It may not be the best solution, but I cannot think of something better right now.
In the pre-execution I create the grid you want, and in the layout this grid-array is displayed.
<?php
if( isset($_POST['groups'])){
$groups = $_POST['groups'];
$subject = $_POST['subject'];
$sql="SELECT
a.groupcode, a.groupstudents, a.studentid,
b.groupcode, b.coursename, b.studentid, b.date, b.class1, b.attend, b.attendno
FROM table_1 a, table_2 b
WHERE b.groupcode = '$groups' AND b.coursename = '$subject' AND
(a.studentid = b.studentid AND a.groupcode = b.groupcode)";
$result=mysqli_query($GLOBALS["___mysqli_ston"], $sql);
$dates = array();
$display = array();
while ($rows=mysqli_fetch_array($result)) {
if (!isset($display[$rows['groupstudents']])) {
$display[$rows['groupstudents']] = array();
}
if (!isset($dates[strtotime($rows['date'])])) {
$dates[strtotime($rows['date'])] = count($dates);
}
$class1 = $rows['class1'];
if ($class1 == 0) $class1 = "No Class"; if ($class1 == 1) $class1 = "Absent";
if ($class1 == 3) $class1 = "Present"; if ($class1 == 2) $class1 = "Late";
$display[$rows['groupstudents']][$dates[strtotime($rows['date'])]] = $class1;
}
echo '<table width="100%" border="1" cellspacing="0" cellpadding="3">';
echo '<tr>';
echo '<td align="center"><strong><font size="2">Students</font></strong></td>';
foreach ($dates as $date => $reversedIndex) {
echo '<td align="center"><strong><font size="2">' . date("d-F-Y", $date) . '</font></strong></td>';
}
echo '</tr>';
foreach ($display as $student => $row) {
echo '<tr>';
echo '<td align="center"><font size="2">' . $student . '</font></td>';
foreach ($dates as $date => $index) {
echo '<td align="center"><font size="2">';
if (isset($row[$index])) {
echo $row[$index];
} else {
echo '';
}
echo '</font></td>';
}
echo '</tr>';
}
echo '</table>';
?>