Nested comments in PHP & MySQL

Question

I searched through the forums but couldn\'t get an authoritative answer. I want to implement a nested comment structure in a way like this:

    &l         


        

Answer 1

There are several different ways to store heirarchical data in MySQL. Check out Bill Karwin's presentation that demonstrates four options.

• Adjacency List
• Path Enumeration
• Nested Sets
• Closure Table

---

You are using the adjacency list model for storing heirarchical data, but unfortunately this is the hardest model you could choose for querying subtrees.

Your options are:

• Change to a different model.
• Restrict queries to n levels deep.
• Use a stored procedure to query recursively. For more information about this, see Quassnoi's series of articles - Hierarchical queries in MySQL.

Answer 2

I had done something similar for my blogpost. Yet, I just tried out with the same data. When you say nested comments it is better you can use nested functions this way:

function getComments($parent)
{
    # Get the data from SQL.
    # Check if it has nested comments.
    if (hasComments())
        getComments($child); # $child is the ID of the current comment.
}

To make it this way, I have imported your data to MySQL and tried this:

<?php
    mysql_connect('localhost', 'root');
    mysql_select_db('nestedcomments');
    function getComments($parent)
    {
        $res = mysql_query("SELECT * FROM `nestcomm` WHERE `parent` = $parent");
        if (mysql_num_rows($res))
        {
            echo "<ul>\n";
            while (($dat = mysql_fetch_array($res)) !== false)
                echo "<li>", $dat["text"], getComments($dat["id"]), "</li>\n";
            echo "</ul>\n";
        }
        else
            echo ($parent === 0) ? 'No Comments!' : "";
    }
    getComments(0);
?>

As I said before I have used nested functions, and as you asked the output is almost same (without the braces) this way:

<ul>
<li>This is the parent first comment!<ul>
<li>This is the reply for the first parent comment!<ul>
<li>This is a reply for the first reply of the parent comment!</li>
<li>This is a third reply for the first parent comment!</li>
</ul>
</li>
<li>This is another reply for first parent comment!</li>
</ul>
</li>
<li>This is gonna be parent second comment!<ul>
<li>This is a reply for the second comment!</li>
</ul>
</li>
<li>This is fourth parent comment!</li>
</ul>

Hope this helps out.