JSON data from php not outputting

Question

I am running into an issue getting JSON data that is sent from a php file to output onto my page. What I am trying to do is create a commenting system, so whenever someone makes a comment, my AJAX code gets the SELECT query results and reloads the already listed comments, essentially to show new comments, whether the user posted it or someone else did.

What I have is three files, the comments page, AJAX, and PHP files. I do a SELECT query initially on the comments page to get the data on page load, then I want the same set of comments to consistently load every three seconds.

The setInterval() is working and the JSON is being sent over, as I see it within my console, but it isn't actually refreshing and outputting. In addition, I really only want the comments to reload if there has been a new comment created, rather than the comments reloading just to reload.

Does anyone seeing what I am doing wrong for the JSON data to not output?

Here is how I initially get the output on the page load. This is solely using the php on the comments page.

<div id="comment-container">
<?php
$select_comments_sql = "
    SELECT c. *, p.user_id, p.img
    FROM home_comments AS c
    INNER JOIN (SELECT max(id) as id, user_id 
                FROM profile_img 
                GROUP BY user_id) PI
      on PI.user_id = c.user_id
    INNER JOIN profile_img p
      on PI.user_id = p.user_id
     and PI.id = p.id
    ORDER BY c.id DESC
";

  if ($select_comments_stmt = $con->prepare($select_comments_sql)) {
        $select_comments_stmt->execute();
        if (!$select_comments_stmt->errno) {
            //echo "error";
        }
        $select_comments_stmt->bind_result($comment_id, $comment_user_id, $comment_username, $home_comments, $comment_date, $commenter_user_id, $commenter_img);
    //var_dump($select_comments_stmt);  
        $comment_array = array();
        while ($select_comments_stmt->fetch()) {
            $comment_array[] = $comment_user_id;
            $comment_array[] = $comment_username;
            $comment_array[] = $home_comments;
            $comment_array[] = $comment_date;
            $comment_array[] = $commenter_user_id;
            $comment_array[] = $commenter_img;
            $commenter_img = '<img class="home-comment-profile-pic" src=" '.$commenter_img.'">';
            if ($home_comments === NULL) {
                echo 'No comments found.';
            } else {
                echo '<div class="comment-post-box" id="comment-'. $comment_id .'">';
                //echo '<div class="comment-post-box" id="comment-'.$row['id'].'">';
                echo $commenter_img;
                echo '<div class="comment-post-username">'.$comment_username. '</div>';
                echo '<div>'.$comment_date. '</div>';
                echo '<div class="comment-post-text">'.$home_comments. '</div>';
                echo '</div>';
            }
        }
  }
?>
        </div>

The PHP to SELECT from the home_comments table and echos the JSON

$user = new User();

        //Get the last insert id
            $select_comments_sql = "
            SELECT c. *, p.user_id, p.img
            FROM home_comments AS c
            INNER JOIN (SELECT max(id) as id, user_id 
                        FROM profile_img 
                        GROUP BY user_id) PI
              on PI.user_id = c.user_id
            INNER JOIN profile_img p
              on PI.user_id = p.user_id
             and PI.id = p.id
            ORDER BY c.id DESC
        ";

        if ($select_comments_stmt = $con->prepare($select_comments_sql)) {
            //$select_comments_stmt->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $select_comments_stmt->execute();
            $rows = $select_comments_stmt->fetchAll(PDO::FETCH_ASSOC);
            $comments = array();
            foreach ($rows as $row) {

                    $html = "";
                    //$html .= '<div class="comment-post-box">';
                    $html .= '<div class="comment-post-box" id="comment-'.$row['id'].'">';
                    $html .= '<img class="home-comment-profile-pic" src="'.$row['img'].'">';
                    $html .= '<div class="comment-post-username">'.$row['username']. '</div>';
                    $html .= '<div>'.$row['date']. '</div>';
                    $html .= '<div class="comment-post-text">'.$row['comment']. '</div>';
                    $html .= '</div>';
                    $data = array('id' => $row['id'], 'date' => $row['date'], 'html' => $html);
                    $comments[] = $data;
            }
        }
                echo json_encode($comments);

Then my AJAX to attempt to refresh the list of comments:

function commentRetrieve(){

    $.ajax({ 
            url: "ajax-php/comment-retrieve.php",
            type: "get",
            success: function (data) {
              //console.log(data);
                if (data == "Error!") {
                    alert("Unable to retrieve comment!");
                    alert(data);
                } else {
                    var array = JSON.parse(data);
                    console.log(data);
                    $(array).each(function(this) {
                        if($('#comment-' + this.id).length == 0) {
                            $('#comment-container').prepend(this.html);
                            console.log(this.html);
                        }
                    });
                }
            },
            error: function (xhr, textStatus, errorThrown) {
                alert(textStatus + " | " + errorThrown);
                console.log("error"); //otherwise error if status code is other than 200.
            }
        });


}
setInterval(commentRetrieve, 3000);

Edit: DATA sent over

[{id: "51", date: "2016-10-26 09:25:42",…}, {id: "22", date: "0000-00-00 00:00:00",…},…]
0
:
{id: "51", date: "2016-10-26 09:25:42",…}
1
:
{id: "22", date: "0000-00-00 00:00:00",…}
2
:
{id: "21", date: "0000-00-00 00:00:00",…}
3
:
{id: "20", date: "0000-00-00 00:00:00",…}
4
:
{id: "19", date: "2016-10-23 09:56:08",…}
5
:
{id: "18", date: "2016-10-21 09:51:35",…}
6
:
{id: "16", date: "2016-10-20 14:41:10",…}
7
:
{id: "15", date: "2016-10-20 13:23:30",…}
8
:
{id: "12", date: "2016-10-20 09:10:28",…}
9
:
{id: "11", date: "2016-10-19 23:54:58",…}
10
:
{id: "10", date: "2016-10-19 23:41:52",…}
11
:
{id: "9", date: "2016-10-19 23:41:52",…}
12
:
{id: "8", date: "2016-10-19 23:41:16",…}

Where I received ^^

Answer 1

Small working example:

 var count = 0; var RETRIEVE_INTERVAL = 1000; var datas = [ '[{"id": "51", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-51\\\\">51</div>"}]' , '[{"id": "22", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-22\\\\">22</div>"}]' , '[{"id": "5", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-5\\\\">5</div>"}]' , '[{"id": "34", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-34\\\\">34</div>"}]' , '[{"id": "51", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-51\\\\">51</div>"}]' , '[{"id": "10", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-10\\\\">10</div>"}]' , '[{"id": "70", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-51\\\\">70</div>"}]' , '[{"id": "22", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-22\\\\">22</div>"}]' , '[{"id": "40", "date": "2016-10-26 09:25:42", "html": "<div id=\\\\"comment-40\\\\">40</div>"}]' ]; function commentRetrieve(){ // mock data retrieval if (count == datas.length) return; var data = datas[count++]; var array = JSON.parse(data); $(array).each(function() { if($('#comment-' + this.id).length == 0) { $('#comment-container').prepend(this.html); } }); setInterval(commentRetrieve, RETRIEVE_INTERVAL); } $(commentRetrieve); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <body> <div id="comment-container" id="intro-box"> <div id="comment-5">5</div> <div id="comment-10">10</div> </div> </body>