Question

i have this js piece of code:

<script language="JavaScript" type="text/javascript">
    var sendReq = getXmlHttpRequestObject();
    var receiveReq = getXmlHttpRequestObject();
    var lastMessage = 0;
    var mTimer;
    function handleReceiveChat() 
    {
       if (receiveReq.readyState == 4)
       {
          var chat_div = document.getElementById('div_chat');    
          var xmldoc = receiveReq.responseXML;     
          var message_nodes = xmldoc.getElementsByTagName("message");
          //more code
       }
    }


    function getChatText()
    {
        if (receiveReq.readyState == 4 || receiveReq.readyState == 0) 
        {
           receiveReq.open("GET", 'getChat_xml.php?chat=1&last=' + lastMessage, true);
           receiveReq.onreadystatechange = handleReceiveChat; 
           receiveReq.send(null);
        }
    }
</script>

and in getChat_xml i have this:

$xml = '<?xml version="1.0" ?><root>';
if(!isset($_GET['chat'])) 
{
$xml .='Your are not currently in a chat session.  <a href="">Enter a chat session here</a>';
$xml .= '<message id="0">';
$xml .= '<user>Admin</user>';
$xml .= '<text>Your are not currently in a chat session.  &lt;a href=""&gt;Enter a chat session here&lt;/a&gt;</text>';
$xml .= '<time>' . date('h:i') . '</time>';
$xml .= '</message>';
}
else
{
$last = (isset($_GET['last']) && $_GET['last'] != '') ? $_GET['last'] : 0;
$sql = "SELECT message_id, user_name, message, date_format(post_time, '%h:%i') as post_time" . 
    " FROM message WHERE chat_id = " . db_input($_GET['chat']) . " AND message_id > " . $last;
$message_query = db_query($sql);
//Loop through each message and create an XML message node for each.
while($message_array = db_fetch_array($message_query))
    {
    $xml .= '<message id="' . $message_array['message_id'] . '">';
    $xml .= '<user>' . htmlspecialchars($message_array['user_name']) . '</user>';
    $xml .= '<text>' . htmlspecialchars($message_array['message']) . '</text>';
    $xml .= '<time>' . $message_array['post_time'] . '</time>';
    $xml .= '</message>';
}
}
$xml .= '</root>';

can anybody help here please?? dont understand how this works
thanks

Answer 1

After seeing the code you have posted, these problems come to mind…

1. You have not actually added an echo $xml; to output the generated XML.
2. Even after adding an ‘echo’ statement, you may get null responseXML (and hence an undefined getElementsByTagName) because of some errors in your PHP code (maybe the SQL query).
3. Even if your PHP code is right, you will get null responseXML because u have not sent proper content header (header('Content-Type: text/xml');).