[code]function getPublishedPostsByCategory($category_id) {
    global $conn;
    $sql = "SELECT * FROM posts ps
            WHERE ps.id IN
            (SELECT pt.post_id FROM post_category pt
                WHERE pt.category_id=$category_id GROUP BY pt.post_id
                HAVING COUNT(1) = 1)";
    $result = mysqli_query($conn, $sql);
    // fetch all posts as an associative array called $posts
    $posts = mysqli_fetch_all($result, MYSQLI_ASSOC);

    $final_posts = array();
    foreach ($posts as $post) {
        $post['category'] = getPostCategory($post['id']);
        array_push($final_posts, $post);
    }
    return $final_posts;
}[/code]