[SOLVED] How do I log users out after they have closed the browser?

dpacmittal · March 16, 2009

hum...if my test script worked on your xamp, then it's not the server. what is your current code for retrieve.php? where does the posted message go (aka does retrieve.php handle that too)?

retrieve.php:

<?php
session_start();
$id=$_SESSION['id'];
include("connect.php");
ob_implicit_flush(true);

$curr_time=time();
$updquery=mysql_query("Update users set lastactive='$curr_time' where user_id='$id'");
$delquery=mysql_query("delete from users where (lastactive+20)<'$curr_time'",$con);
$lastmsg=$_SESSION['lastmsg'];

for($i=1;$i<=20;$i++)
{
$q=mysql_query("Select Max(lineno) from abc");
$row2=mysql_fetch_row($q);
if($row2[0]==$lastmsg)
{
usleep(1000000);
}
else
{
$res1=mysql_query("Select * from abc where lineno>'$lastmsg' and lineno<='$row2[0]' order by lineno ASC");
while($row = mysql_fetch_array($res1))
{
echo $row['line']."<hr width=97% size=1 noshade>";
}
$_SESSION['lastmsg']=$row2[0];
exit;
}
}
?>

retrieve.js:

function sendpost() {
var txt=document.chat.line.value;
document.chat.line.value="";
$.post("post.php", { line: txt } );
}


function sub(e) {
var keycode= e.which?e.which:window.event.keyCode;
if(keycode==13)
sendpost();
}


function retrieve()
{$.ajax({
  type: "GET",
  url: "retrieve.php",
  success: function(data) {
$("#chatwin").append(data);
},
complete: function(xhr,status) {
if(status=="success")
retrieve();
}
});
}


function startRetrieve() {
setInterval("user_fetch()",1000);
retrieve();
}

function user_fetch()
{
var uf=new httprequest();
var url="User_online.php";
uf.open("GET",url,true);
uf.onreadystatechange=function() {
if(uf.readyState==4 && uf.status==200)
{
document.getElementById("online_list").innerHTML=uf.responseText;
}
}
uf.send(null);
}

chat.php (the main file which user loads in the browser) :

<?
session_start();
if(isset($_SESSION['uname']) && isset($_SESSION['id']))
{
$id=$_SESSION['id'];
$uname=$_SESSION['uname'];
include("connect.php");
$q=mysql_query("select * from users where user_id='$id' and user_name='$uname'");
if(mysql_num_rows($q))
{
?>
<html>
<head>
<script type="text/javascript" src=xmlobject.js></script>
<script type="text/javascript" src=jquery.js></script>
<script type="text/javascript" src=retrieve.js></script>
<style type="text/css">
<!--
#online_list {
position:absolute;
width:200px;
height:531px;
z-index:1;
left: 1045px;
top: 18px;
background-color: #000000;
color: #FF9900;
}
#chatwin {
position:absolute;
width:1000px;
height:432px;
z-index:2;
left: 13px;
top: 13px;
color: #6633CC;
background-color: #000000;
	overflow:auto;
padding:10px;
}
body {
background-color: #333333;
}
#logoffLink {
position:absolute;
width:44px;
height:25px;
z-index:3;
left: 126px;
top: 447px;
}
#autoscroll {
position:absolute;
width:109px;
height:25px;
z-index:4;
left: 14px;
top: 447px;
}
#msgbox {
position:absolute;
width:646px;
height:54px;
z-index:5;
left: 14px;
top: 482px;
}

-->
</style>

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"></head>
<body onload=startRetrieve()>

<div id="chatwin">
</div>
<div id="autoscroll">
  <form name=autoscr>
    <input name="scr" type="checkbox" value="" checked>
    Auto Scroll
  </form>
</div>
<div id="logoffLink"><a href="javascript:window.open('','_parent','');window.close();">Logoff</a></div>

  <div id="msgbox">
    <form name="chat" onKeyPress="sub(event)">
  <textarea name="line" cols="100"></textarea>
  <input type="button" value="Send" onClick=sendpost()>
</form>
</div>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <p> </p>
  <div id="transcript"></div>
  <div id="online_list"></div>

</body>
</html>
<?
}
else
{
unset($_SESSION);
session_destroy();
header('location:login.php');
}
}
else
{
header('location:login.php');
}
?>

You were wrong when you said usleep(1000) delays 1 second. I referred to the php manual, it said usleep takes microseconds as arguments.

Interesting thing is when I put usleep(1000) instead of usleep(1000000), the script works fine. Which means that message is posted only after execution of retrieve.php completes.

rhodesa · March 16, 2009

You were wrong when you said usleep(1000) delays 1 second. I referred to the php manual, it said usleep takes microseconds as arguments.
Interesting thing is when I put usleep(1000) instead of usleep(1000000), the script works fine. Which means that message is posted only after execution of retrieve.php completes.

oops, got my microseconds & milliseconds mixed up

not sure then. i don't see anything that is wrong with the code.

dpacmittal · March 16, 2009

not sure then. i don't see anything that is wrong with the code.

Yeah, nothing wrong with the code. I found out the solution. After 3 days of googling, I finally found one website which has something about my problem.

http://www.ovalpixels.com/blog/2008/11/15/highly-responsive-ajax-applications-without-excess-bandwidth-waste/

Just have a look and you'll learn something new. PHP's inbuilt session handler won't allow two php scripts that use same sessions run simultaneously. It will just queue them until the previous file has completed executing. That was hell of a problem. I couldn't have thought about that.

I feel like sh*t.

Thanks for your regular response. You helped a lot.

rhodesa · March 16, 2009

And, if you hadn’t read this post, you’d have had some hard time finding this out. It is just that in every normal application, you can be 97% sure you will be using sessions. And in most of the time, you will rely on the built-in php sessions’ handler. So far, so good. But the small problem is that you cannot simultaneously be running different scripts ( or more than one instantiation of a script ) which use one and the same user session ( that, again, was a discovery by Mr. Pagebaker ). PHP will just queue all subsequent requests which try to interact with that session, until the first one has been closed. Well, that is not much of an asynchroneous technique either then. Getting back to our chat application - if you want to long-poll the server and wait for new messages ( what we will call read() ) and simultaneously send new messages to the server ( write() ), the application will not write() until the read() request has finished ( which we have set to 5 mins, if in the worst case there is no new data to be received ) - that is absolutely not what we need.

wow...how did i not know that! i can't believe i haven't run into that issue before. i wonder if you could work around it with cookies instead

dpacmittal · March 16, 2009

I couldn't think, even in my dreams, that sessions would be causing such a problem. There's a workaround using cakephp (actually database based sessions) which is mentioned on the same page which I provided link to.The workaround is also on the same page. Hopefully, I would be able to resume the development of my application now, which was stopped due to this problem.

Thanks, again.

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[SOLVED] How do I log users out after they have closed the browser?

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