[RESOLVED] XMLHttpRequest retrieve variables?

what i'm trying to do is find all results that come after the page has loaded...

the <div id="last">32</div> is the latest id that is displayed on the page, this i will have done with php later, but what i want to do, is when retrieving the data back from test.php i want this number to be replaced with $lastmessage which comes from test.php

my question is: how do i retrieve the data as variables, so that i can replace the innerHTML of div id=last with only the variable $lastmessage, and add $messages to the div id=messages

my code:

index.php

HTML Code:

---

<script type="text/javascript">
        function refreshMessages(lastID) {
                if (lastID.length==0) {
                        document.getElementById("messages").innerHTML="";
                return; 
                }
                if (window.XMLHttpRequest) {
                        xmlHttp=new XMLHttpRequest(); 
                } else { 
                        xmlHttp=new ActiveXObject("Microsoft.XMLHTTP"); 
                }
                var url="test.php?q=" + lastID;
                xmlHttp.open("GET",url,false);
                xmlHttp.send();
                e = document.getElementById("messages");
                e.innerHTML=e.innerHTML+xmlHttp.responseText;
        }
</script>
<div id="last">32</div>
<input type="button" onclick="refreshMessages(document.getElementById('last').innerHTML);" value="Click"/>
<div id="messages"></div>

---

test.php

PHP Code:

---

<?php
include("config.php"); // config.php only connects to the database

$query_string = mysql_real_escape_string($_GET['q']);

$res = mysql_query("SELECT * FROM chat WHERE id>'" . $query_string . "'") or die(mysql_error());
$rowCount = mysql_num_rows($res);

if ($rowCount < 1) {
} else {
$messages = ""; // define the variable
    while($row = mysql_fetch_array($res)) {
    $uid = $row['userid'];
        $res2 = mysql_query("SELECT * FROM login WHERE uid='" . $uid . "'") or die(mysql_error());
        while($row2 = mysql_fetch_array($res2)) {
        $username = $row2['display'];
        }
    $time = $row['date'];
    $message = $row['message'];
    $messages .= '<p style="padding:0px;margin:0px;margin-top:3px;width:380px;text-indent:5px;">' . $username . ' - [<font style="font-size:11px;">' . date("H:i - d/m", $row['date']) . '</font>]<br /><font style="margin-left:10px;">' . $row['message'] . '</font></p>';
    $lastmessage = $row['id'];
    }
    echo $messages;
}
?>

---

Use PHP's json_encode() to return your data as JSON:

PHP Code:

---

    //at the end of your code:
    //echo $messages;
    echo json_encode(array('lastmessage'=>$lastmessage, 'messages'=>$messages));
}
?> 


---

This will echo something like:

Code:

---

{"lastmessage":"32","messages":"<p>...</p>"}

---

...which Javascript can make use of like this:

Code:

---

var jsonResponse = JSON.parse(xmlHttp.responseText);
alert(jsonResponse['lastmessage']); //32

---

perfect! thanks, just what i needed, works like a charm.

apparently i can't rate the post

edit: sorry forgot to mark as resolved