How can I update/insert multiple tasks in my DB?

I have this code

// home.view.php main view file

<table>
  <thead>
    <tr>
      <?php foreach($taskName as $task): ?>
        <th><?= strtoupper($task->Field) ?></th>
      <?php endforeach; ?>
    </tr>
  </thead>
  <tbody>
    <?php foreach($taskList as $task): ?>
        <tr>
          <form class="" action="update.php" method="post">
            <td>
                <label for="id"><?= $task->id ?></label>
                <input type="checkbox" name="id[]" value="<?= $task->id ?>" />
            </td>
            <td>
                <label for="description"></label>
                <input type="text" name="description" value="<?= $task->description ?>" />
            </td>
            <td>
                <label for="completed"></label>
                <input type="checkbox" name="completed" <?= $task->completed ? 'checked value="true"' : '' ?> />
            </td>
          </form>
          <form action="delete.php" method="post">
          <td><button type="submit" name="delete" value="<?= $task->id ?>">delete</button></td>
          </form>
        </tr>
    <?php endforeach; ?>
  </tbody>
</table>

logic is

// update.php

<?php

require_once 'functions.php';
require_once 'config.php';

if(isset($_POST['completed'])) {
    $completed = $_POST['completed'] == 'on' ? 1 : 0;
} else $completed = 0;

$id = $_POST['id'];
$description = htmlentities($_POST['description']);

$query = $dbh->prepare('update todos set description = :description, completed = :completed where id = :id');
$query->execute(array(':description' => $description, ':completed' => $completed, ':id' => $id));

header('Location: index.php');

I tried to insert array of checkboxes, but I don't know how to retrieve all of them in the post, because when I submit a form, I can do only one at a time. Thing is I'm just learning, so if you have advice I will be grateful.

**Edited: removed dd() function for checking $_POST value