long-polling info from mysql not working

I'm trying to make long-polling based chat with ajax, jquery, php and mysql, but something seems wrong (also i'm new to long-polling).

index.php:

 <?php
include 'db.php';
$result = mysql_query("SELECT id FROM chatpoll ORDER BY id DESC LIMIT 1");
while($row = mysql_fetch_array($result))
{
    $old_msg_id = $row['id'];
}
?>
<html>
<head>
    <script src="http://jqueryjs.googlecode.com/files/jquery-1.3.2.min.js" type="text/javascript" charset="utf-8"></script>
    <script type="text/javascript" charset="utf-8">

        var old_msg_id = <?php echo $old_msg_id; ?>;

        function waitForMsg(){
            $.ajax({
                type: "GET",
                url: "poll.php?old_msg_id=" + old_msg_id,
                async: true,
                cache: false,

                success: function(data){
                    var json = eval('(' + data + ')');
                    if(json['msg'] != "") {
                        alert("New msg added to base!");
                    }
                    old_msg_id = json['old_msg_id'];
                    setTimeout('waitForMsg()',1000);
                },
                error: function(XMLHttpRequest, textStatus, errorThrown){
                    alert("error: " + textStatus + " (" + errorThrown + ")");
                    setTimeout('waitForMsg()',15000);
                }
            });
        }
        $(document).ready(function(){
            waitForMsg();
        });
        function load(old_msg_id) //part of code which i'm not using yet
        {
            $.get('getmsg.php?last_msg_id='+ old_msg_id, function(data){
                $('#chat').append(data);
            }, 'html');
        }
    </script>
</head>
<body>
    <div id="chat">
    </div>
</body>
</html>

and poll.php

 <?php
include 'db.php';
$old_msg_id = $_GET['old_msg_id'];
$result = mysql_query("SELECT id FROM chatpoll ORDER BY id DESC LIMIT 1");
while($row = mysql_fetch_array($result))
{
    $last_msg_id = $row['id'];
}
while($old_msg_id >= $last_msg_id) {
    usleep(1000);
    clearstatcache();
    $old_msg_id = $last_msg_id;
}
$response = array();
$response['msg'] = 'new';
$response['old_msg_id'] = $old_msg_id;
echo json_encode($response);
?>

it's not showing any error both in index.php and poll.php, but when i insert data with bigger id than old_msg_id nothing happens..

Change code in your poll.php file to following:

<?php
include 'db.php';
$old_msg_id = $_GET['old_msg_id']; 
$result = mysql_query("SELECT id FROM chatpoll ORDER BY id DESC LIMIT 1");
while($row = mysql_fetch_array($result))
{
    $last_msg_id = $row['id']; 
}
while($last_msg_id <= $old_msg_id)
{
    usleep(1000);
    clearstatcache();
    $result = mysql_query("SELECT id FROM chatpoll ORDER BY id DESC LIMIT 1");
    while($row = mysql_fetch_array($result))
    {
        $last_msg_id = $row['id'];
    }
}
$response = array();
$response['msg'] = 'new';
$response['old_msg_id'] = $last_msg_id;
echo json_encode($response);
?>

来源：https://stackoverflow.com/questions/11453423/long-polling-info-from-mysql-not-working

标签

php

jquery

mysql

ajax

long-polling