更新标签内的变量而不刷新

Question

Simply, I want to display the number of unread messages in a label inside the menu as follows:

 <li><a id="2" style="background-image:url('menu icons/comments.png'); background-repeat: no-repeat; background-position: left; background-position-x: 5px;"
                       href= "viewMessages.php">Messages<label id="num_msg">(<?php echo $count; ?>)</a></li>

where i get $count as:

$num_messages = mysql_query("SELECT COUNT(m.message_id) as cnt FROM messages m INNER JOIN member_message_member mmm ON (m.message_id = mmm.message_id)
                    WHERE mmm.member_id2 = $id AND m.seen = 0") or die(mysql_error());
                    $Mcount = mysql_fetch_assoc($num_messages);
                    $count = $Mcount['cnt'];

and then when a user clicks on a message:

 $("#sub a").click(function(){
                    mesg_id = $(this).attr('msg_id');
                    page = $(this).attr('href')
                    id = $(this).attr('mID');
                    $.ajax ({
                            data: {message_id:mesg_id},
                            type: 'POST',
                            url:  'Seen_messages.php',
                            success: function(response) {
                                if (response == 1) {

                                } else {
                                    alert(response);
                                }
                            }
                        });
                });

Seen_messages.php:

@mysql_connect("localhost", "root", "") or die(mysql_error());
    mysql_select_db("mydb") or die(mysql_error());
    $message_id = $_POST['message_id'];
   mysql_query("UPDATE `messages` SET `messages`.`seen` = TRUE WHERE message_id={$message_id}") or die (mysql_error());
   echo "1";

everything is working properly, except that I have to refresh the page to update $count, So is there anyway to update the variable inside the label without manual refresh?

Answer 1

Make Seen_messages.php respond with the updated unread count, instead of always 1, then use that response to update the user interface:

// ...
success: function(response) {
   if (isNaN(response)) {
       alert('Error!');
   } else {
       $('#num_msg').text(response);
   }
}