Recursive function for nested comments in php

I am trying to display nested comments with php. Each comment has an id and parent_id. The main comments have a parent_id of 0 while the replies have a a parent_id that equals the id of the comment that was replied to. For example if we do comment id:50, we should be calling the recursive function, making the new parent_id 50.When our foreach gets to comment id:58, it should pass the if (50 == 50) and be displayed with an indent. The problem I am experiencing is the recursive function isn’t being called at all, and I’m only seeing the main comments (those with a parent_id of 0).

  if($result) 
  {
    $commentsArr = mysqli_fetch_all($result, MYSQLI_ASSOC);
    echo displayIndentedComments($commentsArr);
  }


  function displayIndentedComments($commArr, $parent_id = 0, $indent = 0) 
  {
    
    $commentHTML = '';
    
    foreach ($commArr as $comment) 
    {

      $username = $comment['username'];
      $timestamp = date("M j, Y, h:i A", strtotime($comment['submit_date']));
      $commentText = $comment['content'];
      $commentId = $comment['id'];
      $commentParentId = $comment['parent_id'];
            
      if($commentParentId == $parent_id) 
      {
        
        $marginLeft = 10 * $indent;
        $marginLeftAttr = $marginLeft . 'px';
        $commentHTML .= "<div id='$commentId' style='margin-top: 30px; margin-bottom: 30px; margin-left: $marginLeftAttr;'>
          <b style='color: LightSeaGreen;' >$username</b> - <span style='font-size: 13px';>$timestamp</span><br>
                
          <div class='container m-0 p-0'  style='max-width: 900px;'>
            <div class='row'>
              <div style='margin: auto;' class='col-9'>
                <div class='mt-1'>$commentText</div> 
            </div>
              <div class='col-3' style='text-align: right;'>
                <button id='replyButton' onclick='showReplyCommentBox(this)' style='background: none; border: none;'><i class='fa fa-reply' aria-hidden='true'></i></button>
              </div>
            </div>
          </div>
                
          <p class='border-bottom mt-2'></p>
        </div>
      ";
      
        displayIndentedComments($commArr, $commentId, $indent + 1);
      }
    }
          
    return $commentHTML;
  }

{"id":"60","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 13:00:01"}
{"id":"59","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 12:58:52"}
{"id":"58","page_id":"1","parent_id":"50","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 12:56:10"}
{"id":"57","page_id":"1","parent_id":"53","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 12:55:50"}
{"id":"56","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:49:12"}
{"id":"55","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:45:44"}
{"id":"54","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:38:11"}
{"id":"53","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:37:02"}
{"id":"52","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:08:56"}
{"id":"51","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 11:01:50"}
{"id":"50","page_id":"1","parent_id":"0","username":"abc","content":"Lorem ipsum","submit_date":"2023-11-10 10:59:13"}

>Solution :

When you make the recursive call, you’re not doing anything with the result. It needs to be added to the output string.

Change

displayIndentedComments($commArr, $commentId, $indent + 1);

to

$commentHTML .= displayIndentedComments($commArr, $commentId, $indent + 1);