// simple AJAX API 

function ajax () {
    this.message_loading   = '<div style="text-align: center;"><img src="images/ladekreis.gif" width="50" height="50" alt="" /></div>';
    this.message_no_result = "An error has occured :-(";
    
    this.http_request      = false;
    
    this.request = function (url, output_id) {
        document.getElementById(output_id).innerHTML = this.message_loading;
        
        if(window.XMLHttpRequest) { // Mozilla, Safari,...
            http_request = new XMLHttpRequest();
        }
        else if(window.ActiveXObject) { // IE
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            }
            catch (e) {
                try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
                }
                catch (e) {}
            }
        }
        
        if(!http_request) {
            return false;
        }
        
        http_request.onreadystatechange = function() {
            if(http_request.readyState == 4) {
                if(http_request.status == 200) {
                    handle_http_response(http_request.responseText, output_id);
                }
                else {
                    return false;
                }
            }
            else {
                return false;
            }
        }
        
        http_request.open('get', url, true);
        http_request.send(null);
    }
    
    var handle_http_response = function (content, output_id) {
        if(!document.getElementById)
            return false;
        if(!document.getElementById(output_id))
            return false;
        if(content == "FALSE")
            document.getElementById(output_id).innerHTML = this.message_no_result;
        else
            document.getElementById(output_id).innerHTML = content;
    }
}