[p-book] category

<?php
declare(strict_types = 1);                                    // Use strict types
require 'includes/database-connection.php';                   // Create PDO object
require 'includes/functions.php';                             // Include functions

$id = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT);     // Validate id
if (!$id) {                                                   // If no valid id
    include 'page-not-found.php';                             // Page not found
}

$sql = "SELECT id, name, description FROM category WHERE id=:id;"; // SQL statement
$category = pdo($pdo, $sql, [$id])->fetch();                  // Get category data
if (!$category) {                                             // If category not found
    include 'page-not-found.php';                             // Page not found
}

$sql = "SELECT a.id, a.title, a.summary, a.category_id, a.member_id, 
               c.name AS category,
               CONCAT(m.forename, ' ', m.surname) AS author,
               i.file AS image_file,
               i.alt  AS image_alt 
          FROM article    AS a
          JOIN category   AS c   ON a.category_id  = c.id
          JOIN member     AS m   ON a.member_id    = m.id
          LEFT JOIN image AS i   ON a.image_id     = i.id
         WHERE a.category_id = :id AND a.published = 1
         ORDER BY a.id DESC;";                                // SQL statement
$articles = pdo($pdo, $sql, [$id])->fetchAll();               // Get articles

$sql = "SELECT id, name FROM category WHERE navigation = 1;"; // SQL to get categories
$navigation  = pdo($pdo, $sql)->fetchAll();                   // Get navigation categories
$section     = $category['id'];                               // Current category
$title       = $category['name'];                             // HTML <title> content
$description = $category['description'];                      // Meta description content
?>

<?php include 'includes/header.php'; ?>

<main class="container" id="content">
  <section class="header">
    <h1><?= html_escape($category['name']) ?></h1>
    <p><?= html_escape($category['description']) ?></p>
  </section>
  <section class="grid">
  <?php foreach ($articles as $article) { ?>
    <article class="summary">
      <a href="article.php?id=<?= $article['id'] ?>">
        <img src="uploads/<?= html_escape($article['image_file'] ?? 'blank.png') ?>"
             alt="<?= html_escape($article['image_alt']) ?>">
        <h2><?= html_escape($article['title']) ?></h2>
        <p><?= html_escape($article['summary']) ?></p>
      </a>
      <p class="credit">
        Posted in <a href="category.php?id=<?= $article['category_id'] ?>">
        <?= html_escape($article['category']) ?></a>
        by <a href="member.php?id=<?= $article['member_id'] ?>">
        <?= html_escape($article['author']) ?></a>
      </p>
    </article>
  <?php } ?>
  </section>
</main>

<?php include 'includes/footer.php'; ?>