PHP/MYSQL Comment-reply table structure

Question

I have got a comment script written in PHP working pretty well. It saves the comments in aa mysql comments table with fields for commentid, subjectid, userid and timecreated. I now want to implement a reply function. Should I create a new table of replies with userid, time created, reply and a commentid field.

Or would it be better to just include the replies in the comments table as comments but with two extra fields, one denoting that this particular comment is a reply and the other the comment it is a reply to.

Leaning toward first option but it means extra queries.

Would appreciate any suggestions from those with experience!

Answer 1

I would add two columns for referenceid , and parentid . That way, you can have nested comments, if you so choose. Much easier and more efficient than joining multiple tables in your queries. If the comment is not a reply, referenceid is 0 (or null). No need to create another column to flag whether it's a reply.

Answer 2

This is not an answer to your original question, but I did want to show you a quick and dirty approach to nesting comments that I would use if this were my project. There are almost certainly more elegant methods and another member here might have suggestions.

<?php

// Retrieve ALL comments related to this subject (including all replies and nested comments)
$rs = mysql_query( 'SELECT * FROM `comments` WHERE subjectid = '7' ORDER BY timecreated ASC' );

// Process ALL comments and place them into an array based on their parent id
// Thus we end up with something like:
// $data[ 0 ][ 0 ] = array( 'commentid' => 1, 'subjectid' => 7, 'userid' => 1, 'timecreated' => '2012-05-01 12:00:00', 'parentid' => 0 );
// $data[ 0 ][ 1 ] = array( 'commentid' => 2, 'subjectid' => 7, 'userid' => 5, 'timecreated' => '2012-05-01 14:00:00', 'parentid' => 0 );
// $data[ 2 ][ 0 ] = array( 'commentid' => 3, 'subjectid' => 7, 'userid' => 1, 'timecreated' => '2012-05-01 16:00:00', 'parentid' => 2 ); This is a reply to commentid #2
// $data[ 2 ][ 1 ] = array( 'commentid' => 4, 'subjectid' => 7, 'userid' => 5, 'timecreated' => '2012-05-01 16:30:00', 'parentid' => 2 ); This is another reply to commentid #2
// $data[ 3 ][ 0 ] = array( 'commentid' => 5, 'subjectid' => 7, 'userid' => 3, 'timecreated' => '2012-05-01 17:00:00', 'parentid' => 3 ); This is a reply to the reply with commentid #3

while ( $row = mysql_fetch_assoc( $rs ) ){
    $data[ $row['parentid'] ][] = $row;
}

function output_comments( &$data_array, $parentid ){

    // Loop through all comments with matching $parentid

    foreach ( $data_array[ $parentid ] as $k=>$v ){
        // Output all comments, open .comment DIV but do not close (for nesting purposes)
        echo '<div class="comment"><strong>' . $v['username'] . ':</strong> ' . $v['message'];

        // If there are any replies to this comment, output them by recursively calling this function
        if ( count( $data_array[ $v['commentid'] ] > 0 ){
            output_comments( $data_array, $v['commentid'] );
        }

        // Close the open DIV
        echo '</div>';
    }
}


// Call the output_comments() function, which will recursively run to support unlimited nesting

output_comments( $data, 0 );

You could then style nested comments pretty simply by indenting any DIV.comment who has a parent DIV.comment

<style type="text/css">
.comment .comment {
    padding-left: 30px;
}
</style>