Displaying and linking Foreign Key content in PHP

Question

I am taking some online courses and in one of the exercises we are to create two tables for a blog - blog articles and blog posts - and connect them through a foreign key, then display all content from both. Comments should be linked to a specific article only, while also allowing multiple comments.

My attempt:

function list_articles() { 
    include('core/db/db_connection.php');
    $sql = "SELECT blog.title, blog.content, blog.posted_by, blog.date, article_comments.comments, article_comments.comment_by
            FROM blog LEFT OUTER JOIN article_comments
            ON blog.content_id = article_comments.content_id
            WHERE blog.content != ''
            ORDER BY blog.content_id DESC";
    $result = mysqli_query($dbCon, $sql);
    while ($row = mysqli_fetch_array($result)) {
        echo 
            "<h5 class='posted_by'>Posted by " . $posted_by = $row['posted_by'] . " on " . $row['date'] . "</h5>" . 
            "<h1 class='content_headers'>" . $title = $row['title'] . "</h1>" . 
            "<article>" . $content = $row['content'] . "</article>" . 
            "<div class='commented_by'>Posted by: " . $row['comment_by'] . "</div>" . 
            "<div class='comments'>Comments: " . $row['comments'] . "</div>";
    }
}

And this is how I'm inserting comments in the database:

function insert_comments($comment_by, $comments) {
    include('core/db/db_connection.php');
    $sql =  "SELECT blog.content_id, article_comments.blog_id  
             FROM blog AS blog
             INNER JOIN article_comments AS article_comments ON article_comments.blog_id > blog.content_id";
    mysqli_query($dbCon, $sql);
}

IN PHPMyAdmin the foreign key works alright and the comments are linked to a specific article. I want to transpose this on a web page. When I insert a new article on the page it works alright, but when I try to insert a comment for that article it will not display it.

If I change ON blog.content_id = article_comments.content_id to ON blog.content_id = article_comments.blog_id (blog_id is the field name for the foreign key) - it will display all the comments for an article - but it duplicates that article for each comment associated with it. Does that make any sense? I tried explaining it as best as I can.. Please let me know if you need further clarification. Thanks

By the way, this is the statement I used to create the foreign key:

ALTER TABLE article_comments ADD CONSTRAINT comment_blog_fk FOREIGN KEY (blog_id) REFERENCES wt.blog(content_id) ON DELETE NO ACTION ON UPDATE CASCADE;

EDIT: The result I get with ON blog.content_id = article_comments.blog_id

Article title: LOREM IPSUM
Content: LOREM IPSUM DOLOR SIT AMET....
--------------------------------------
Name: DSK
Comment: Great article!

-- HERE IT DUPLICATES THE ARTICLE TO INSERT A NEW COMMENT --

Article title: LOREM IPSUM
Content: LOREM IPSUM DOLOR SIT AMET....
--------------------------------------
Name: DSK
Comment: Great article! - 2nd comment

As you can see, it duplicates the article for every comment inserted. So I end up with two duplicate articles that hold different comments. If If I'll have 100 comments, the article will get replicated 100 times

The behavior I am expecting:

Article title: LOREM IPSUM
Content: LOREM IPSUM DOLOR SIT AMET....
-------------------------------------- \\ COMMENTS \\
Name: DSK
Comment: Great article!
--------------------------------------
Name: DSK
Comment: Great article! - 2nd comment

Answer 1

Try this:

        $posts = array();
        $pdo = new PDO('mysql:host=localhost;dbname=your_db', 'user', 'password');
        // for example all fields
        $query = $pdo->query('
            SELECT * 
              FROM blog AS blog
             INNER JOIN article_comments AS article_comments ON article_comments.blog_id = blog.content_id
        ');

        while ($row = $query->fetch()) {
            $idContent = $row['content_id'];

            if (!isset($posts[$idContent])) {
                $posts[$idContent] = array(
                    'posted_by' => $row['posted_by'],
                    'title' => $row['title'],
                    'content' => $row['content'],
                    'comments' => array()
                );
            }

            $posts[$idContent]['comments'][] = array(
                'comment_by' => $row['comment_by'],
                'comment' => $row['comment'],
            );

        }

        foreach ($posts as $post) {
            echo '
                Post: ' . $row['title'] . ' . Posted by: ' . $row['posted_by'] .
                '<br/>Content: ' . $row['content'] .
                '<br/>Comments: ';
            ;

            foreach ($post['comments'] as $comment) {
                echo $comment['comment'] . '. Comment by: ' .$row['comment_by'] . '<br/>';
            }

        }