var xmlHttp = createXmlHttpRequestObject();
var from = 0;

function createXmlHttpRequestObject() {
  var xmlHttp;
  if(window.ActiveXObject) {
    try {
      xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch(e) {
      xmlHttp = false;
    }
  } else {
    try {
      xmlHttp = new XMLHttpRequest();
    } catch(e) {
      xmlHttp = false;
    }
  }
  if(!xmlHttp) {
    alert("Error creating the XMLHttpRequest object.");
  } else {
    return xmlHttp;
  }
}

function refreshBanners() {
  if(xmlHttp.readyState == 4 || xmlHttp.readyState == 0) {
    xmlHttp.open("GET", "includes/banners.php?from=" + from + "&self=" + bannerSelf, true);
    xmlHttp.onreadystatechange = handleServerResponse;
    xmlHttp.send(null);
  } else {
    setTimeout("refreshBanners()", 100);
  }
}

function nextBanners() {
  if((from + 4) <= bannerCount) {
    from += 4;
  } else {
    from = 0;
  }
  refreshBanners();
}

function handleServerResponse() {
  if(xmlHttp.readyState == 4) {
    if(xmlHttp.status == 200) {
      if(document.getElementById("bnnr-wrapper")) {
        document.getElementById("bnnr-wrapper")["innerHTML"] = xmlHttp.responseText;
      }
    } else {
      alert("There was a problem accessing the server: "+xmlHttp.statusText);
    }
  }
}