whats wrong with this ?

[wolfe]

i am trying to get the favourite mod from the arcade hack to work on another part of my forum so far php correct but theres a problem with the script the image is not changing on click ? and ideas.

PHP Code:

<script type="text/javascript">

var lastfav;


// Favorites handling.
function favsprocess()
{
    if (xml.handler.readyState == 4 && xml.handler.status == 200 && xml.handler.responseText)
    {
        thisfav = document.getElementById('favs_' + lastfav);
        if (xml.handler.responseText==1)
        {
            thisfav.src = 'images/thread/subfav.gif';
            thisfav.alt = 'Remove Favourite';
            thisfav.title = 'Remove Favourite';
        } else if (xml.handler.responseText==2)
        {
            thisfav.src = 'images/thread/addfav.gif';
            thisfav.alt = 'Add Favourite';
            thisfav.title = 'Add Favourite';
        }
        
    }
}

function dofavs(threadid)
{
    xml = new vB_AJAX_Handler(true);
    xml.onreadystatechange(favsprocess);
    
    lastfav = threadid;
    xml.send('tindex.php', 'do=processfav&threadid=' + threadid);
}


</script>