如何使用foreach正确显示mysql表中的数据？

Question

I'm doing my school's timetable on php page using mysql and I have mysql table like this

klass | day | lesson_name
7A | Monday | lesson1
7A | Monday | lesson5
7A | Monday | lesson3
7A | Tuesday | lesson2
7A | Tuesday | lesson1
7A | Tuesday | lesson4
7A | Wednesday| lesson5
7A | Wednesday| lesson2
7A | Wednesday| lesson1
7A | Thursday | lesson3
7A | Thursday | lesson5
7A | Thursday | lesson4
7А | Friday | lesson2
7А | Friday | lesson3
7А | Friday | lesson5
...And other classes

And this is part of my code:

    <table border="1">
      <tr align=center>
        <th>Monday</th>
        <th>Tuesday</th>
        <th>Wednesday</th>
        <th>Thursday</th>
        <th>Friday</th>
      </tr>
      <?php
        //$con = mysqli_connect("localhost", "user", "password", "database");
        //if (mysqli_connect_errno()) {
        //   echo "Failed to connect to MySQL: " . mysqli_connect_error();
        //}
        $klass = $_POST['klass'];
        $res1 = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass' AND `day` LIKE 'Monday'");
        $res2 = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass' AND `day` LIKE 'Tuesday'");
        $res3 = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass' AND `day` LIKE 'Wednesday'");
        $res4 = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass' AND `day` LIKE 'Thursday'");
        $res5 = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass' AND `day` LIKE 'Friday'");
        foreach ($res5 as $row5) {
            echo "<tr>";
            echo "<td align='center'>$row1[lesson_name]</td>";
            echo "<td align='center'>$row2[lesson_name]</td>";
            echo "<td align='center'>$row3[lesson_name]</td>";
            echo "<td align='center'>$row4[lesson_name]</td>";
            echo "<td align='center'>$row5[lesson_name]</td>";
            echo "</tr>";
        }
      ?>
    </table>

With that code I only display Friday column. I know that the problem is in foreach. I tried to rewrite it as: foreach ($res1 as $row1 and $res2 as $row2 and $res3 as $row3 and $res4 as $row4 and $res5 as $row5), but then it display nothing ;(

How to rewrite my foreach and display all columns&lessons in my timetable correctly?

UPD. I have done as Philipp said, but this code display nothing:

    <table border="1">
      <tr align=center>
        <th>Monday</th>
        <th>Tuesday</th>
        <th>Wednesday</th>
        <th>Thursday</th>
        <th>Friday</th>
      </tr>
      <?php
        //$con = mysqli_connect("localhost", "user", "password", "database");
        //if (mysqli_connect_errno()) {
        //   echo "Failed to connect to MySQL: " . mysqli_connect_error();
        //}
        $klass = $_POST['klass'];
        $res = mysqli_query($con, "SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass'");
        $groupedLessons = array_reduce($res, function($groups, $lesson) {
            if (!array_key_exists($lesson['day'], $groups)) {
                $groups[$lesson['day']] = [];
            }
            $groups[$lesson['day']][] = $lesson;
            return $groups;
        }, []);
        foreach($groupedLessons as $day => $lessons) {
            foreach ($lessons as $lesson) {
            <tr>
                <td><?= $klass ?></td>
                <td><?= $day ?></td>
                <td><?= $lesson['lesson_name'] ?></td>
            </tr>
            }
        }
      ?>
</table>

Answer 1

The best way for you is to make only one DB query, that gets all lessons at once:

SELECT * FROM `Timetable` WHERE `klass` LIKE '$klass'

Then you can group the values based on the week day:

$groupedLessons = array_reduce($allLessons, function($groups, $lesson) {
        if (!array_key_exists($lesson['day'], $groups)) {
            $groups[$lesson['day']] = [];
        }
        $groups[$lesson['day']][] = $lesson;
        return $groups;
    }, []);

Now you can iterate over the data with two nested foreach loops:

foreach($groupedLessons as $day => $lessons) {
    foreach ($lessons as $lesson) {
    ?>
    <tr>
        <td><?= $klass ?></td>
        <td><?= $day ?></td>
        <td><?= $lesson['lesson_name'] ?></td>
    </tr>
    <?php
    }
}