Question

I’m trying to make a commenting thread like Disqus has done. I’m having trouble setting up the logic in PHP to display the comments such that one can reply to each comment and those comments will then stay attached to each other.

here’s my MySQL comments table:

comment_id  comment  item_id  replied_to_id  time
 1           hello1    1          1         1:00pm
 2           hello2    1          1         2:00pm
 3           hello3    1          3         3:00pm
 4           hello4    2          4         4:00pm
 5           hello5    1          2         2:00pm
 6           hello6    1          3         6:00pm

item_id is a column which indicates the parent item that the comments are discussing.

If I pull from my database all the comments with item_id=1, then I’m not sure how to thread them such that the comment_id and replied_to_id‘s are appropriately matched. For example, comment_id=2 should be matched to comment_id=1.

Here’s my PHP:

<?foreach($comments as $row){
  if($row->comment_id==$row->replied_to_id){
    echo $row->comment."-".$row->time; //desired output: hello1-1:00pm    
      foreach($comments as $sub_row){
        if($row->comment_id!=$sub_row->replied_to_id){
           echo $sub_row->comment."-".$sub_row->time;// desired output: hello2-2:00pm
             foreach($comments as $sub_sub_row){
                if($row->comment_id!=$sub_sub_row->replied_to_id){
                  echo $sub_sub_row->comment."-".$sub_sub_row->time;// desired output: hello5-5:00pm  
                }
             } 
        }
     }          
  }
  else{
    echo $row->comment."-".$row->time;   // desired output: hello3-3:00pm
  }
}

This just looks wrong. There has got to be a better way to do this.

Answer 1

Simple demo, not necessarily the most optimal, but working:

function displayComments(array $comments, $parentId = null) {
    foreach ($comments as $comment) {
        if ($comment['replied_to_id'] == $parentId) {
            echo $comment['comment'];
            displayComments($comments, $comment['id']);
        }
    }
}

This assumes top-level comments have no replied_to_id (null). Your example with comment 1 replying to 1 doesn’t make much sense.