Question

我正在使用mysql在php页面上完成学校的时间表，我有像这样的mysql表

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

这是我的代码的一部分：

    <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>

使用该代码我只显示星期五列。我知道问题在于foreach。我尝试将其重写为：foreach（$ res1为$ row1，$ res2为$ row2，$ res3为$ row3，$ res4为$ row4，$ res5为$ row5），但后来没有显示任何内容;（

如何重写我的foreach并正确显示我的时间表中的所有专栏和课程？

UPD。我已经像Philipp说的那样做了，但这段代码没有显示任何内容：

    <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

最好的方法是只进行一次数据库查询，即可立即获取所有课程：

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

然后，您可以根据工作日对值进行分组：

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

现在，您可以使用两个嵌套的foreach循环遍历数据：

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

如何使用foreach正确显示mysql表中的数据？

1 个答案: