使用JSON刷新数据
I am attempting to refresh comments I have on a page every three seconds. However, the code I have isn't refreshing the comments, it is basically outputting the same set of comments I have every three seconds, but it isn't using the classes or img tag I have. It is outputting this every three seconds, over and over again.
Does anyone have any idea why the method I am using is outputting the same set of comments instead of checking for if there is a new one?
AJAX
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);
$(array).each(function($value) {
if($('#comment-container').find('#comment-' + $value.id).length == 0) {
$('#comment-container').prepend($value.html);
}
});
}
},
error: function (xhr, textStatus, errorThrown) {
alert(textStatus + " | " + errorThrown);
console.log("error"); //otherwise error if status code is other than 200.
}
});
}
setInterval(commentRetrieve, 3000);
PHP
if ($select_comments_stmt = $con->prepare($select_comments_sql)) {
//$select_comments_stmt->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$select_comments_stmt->execute();
$rows = $select_comments_stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($rows as $row) {
$comment_id = $row['id'];
$comment_user_id = $row['user_id'];
$comment_username = $row['username'];
$home_comments = $row['comment'];
$comment_date = $row['date'];
$commenter_user_id = $row['user_id'];
$commenter_img = $row['img'];
$commenter_img = '<img class="home-comment-profile-pic" src=" '.$commenter_img.'">';
if ($home_comments === NULL) {
echo 'No comments found.';
} else {
$html = "";
$html .= '<div class="comment-post-box">';
$html .= $commenter_img;
$html .= '<div class="comment-post-username">'.$comment_username. '</div>';
$html .= '<div>'.$comment_date. '</div>';
$html .= '<div class="comment-post-text">'.$home_comments. '</div>';
$html .= '</div>';
$data = array('id' => $comment_id, 'html' => $html);
echo json_encode($data);
}
}
} else {
echo "Error!";
}
Comment page, with initial SELECT query to load comments on page load.
<form action="" method="POST" id="comment-form">
<textarea id="home_comment" name="comment" placeholder="Write a comment..." maxlength="1000" required></textarea><br>
<input type="hidden" name="token" value="<?php echo Token::generate(); ?>">
<input id="comment-button" name="submit" type="submit" value="Post">
</form>
<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">';
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>
You need to change the following thing in your php code:
echo '<div class="comment-post-box">';
with the following:
echo '<div class="comment-post-box" id="comment-'. $comment_id .'">';
Also change this following in your ajax:
if($('#comment-container').find('#comment-' + $value.id).length == 0) {
To this:
if($('#comment-' + $value.id).length == 0) {
Since a id can be just used once on a page we don't care where it is set.
Update 1
Your json code is invalid, so we need to change your php code some bit:
So change this:
foreach ($rows as $row) {
$comment_id = $row['id'];
$comment_user_id = $row['user_id'];
$comment_username = $row['username'];
$home_comments = $row['comment'];
$comment_date = $row['date'];
$commenter_user_id = $row['user_id'];
$commenter_img = $row['img'];
$commenter_img = '<img class="home-comment-profile-pic" src=" '.$commenter_img.'">';
if ($home_comments === NULL) {
echo 'No comments found.';
} else {
$html = "";
$html .= '<div class="comment-post-box">';
$html .= $commenter_img;
$html .= '<div class="comment-post-username">'.$comment_username. '</div>';
$html .= '<div>'.$comment_date. '</div>';
$html .= '<div class="comment-post-text">'.$home_comments. '</div>';
$html .= '</div>';
$data = array('id' => $comment_id, 'html' => $html);
echo json_encode($data);
}
}
To this:
foreach ($rows as $row) {
$comment_id = $row['id'];
$comment_user_id = $row['user_id'];
$comment_username = $row['username'];
$home_comments = $row['comment'];
$comment_date = $row['date'];
$commenter_user_id = $row['user_id'];
$commenter_img = $row['img'];
$commenter_img = '<img class="home-comment-profile-pic" src=" '.$commenter_img.'">';
if ($home_comments === NULL) {
echo 'No comments found.';
} else {
$html = "";
$html .= '<div class="comment-post-box">';
$html .= $commenter_img;
$html .= '<div class="comment-post-username">'.$comment_username. '</div>';
$html .= '<div>'.$comment_date. '</div>';
$html .= '<div class="comment-post-text">'.$home_comments. '</div>';
$html .= '</div>';
$data[] = array('id' => $comment_id, 'html' => $html);
}
}
echo json_encode($data);
So we make just first a array with all comments so the output will be a correct json response to the client.
Update 2:
I have changed your each function some bit:
$(array).each(function(key, value) {
if($('#comment-' + value.id).length == 0) {
$('#comment-container').prepend(value.html);
}
});
Notice the key,value in the function.
After that it was working correctly, I noticed you have to change you comment-retrieve.php since the comments where appending multiple times. You create here your comment div, but without a id. So also change in this file you comment box to echo '<div class="comment-post-box" id="comment-'. $comment_id .'">'; Then it should be working.
You can test it by inserting a new record on your database, or delete a comment in your browser by using web developer tools from your browser or a plugin like firebug.