Why is my long polling code for a notification system not updating in real time? PHP MYSQL
- by tjones
I am making a notification system similar to the red notification on facebook. It should update the number of messages sent to a user in real time. When the message MYSQL table is updated, it should instantly notify the user, but it does not. There does not seem to be an error inserting into MYSQL because on page refresh the notifications update just fine.
I am essentially using code from this video tutorial: http://www.screenr.com/SNH (which updates in realtime if a data.txt file is changed, but it is not written for MYSQL like I am trying to do)
Is there something wrong with the below code:
**Javascript**
<script type="text/javascript">
$(document).ready(function(){
var timestamp = null;
function waitForMsg(){
$.ajax({
type: "GET",
url: "getData.php",
data: "userid=" + userid,
async: true,
cache: false,
success: function(data){
var json = eval('(' + data + ')');
if (json['msg'] != "") {
$('.notification').fadeIn().html(json['msg']);
}
setTimeout('waitForMsg()',30000);
},
error: function(XMLHttpRequest, textStatus, errorThrown){
setTimeout('waitForMsg()',30000);
}
});
}
waitForMsg();
</script>
<body>
<div class="notification"></div>
**PHP***
<?php
if ($_SERVER['REQUEST_METHOD'] == 'GET' )
{
$userid = $_GET['userid'];
include("config.php");
$sql="SELECT MAX(time) FROM notification WHERE userid='$userid'";
$result = mysql_query($sql);
$row = mysql_fetch_assoc($result);
$currentmodif = $row['MAX(time)'];
$s="SELECT MAX(lasttimeread) FROM notificationsRead WHERE submittedby='$userid'";
$r = mysql_query($s);
$rows = mysql_fetch_assoc($r);
$lasttimeread = $rows['MAX(lasttimeread)'];
while ($currentmodif <= $lasttimeread) {
usleep(10000);
clearstatcache();
$currentmodif = $row['MAX(time)'];
}
$response = array();
$response['msg'] = You have new messages;
echo json_encode($response);
}
?>
