var xmlHttp = createXmlHttpRequestObject();

function createXmlHttpRequestObject() 
{	
  // will store the reference to the XMLHttpRequest object
  var xmlHttp;
  // if running Internet Explorer
  if(window.ActiveXObject)
  {
    try
    {
      xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch (e) 
    {
      xmlHttp = false;
    }
  }
  // if running Mozilla or other browsers
  else
  {
    try 
    {
      xmlHttp = new XMLHttpRequest();
    }
    catch (e) 
    {
      xmlHttp = false;
    }
  }
  // return the created object or display an error message
  if (!xmlHttp)
 
    alert("Error creating the XMLHttpRequest object.");
  else 
    return xmlHttp;
}

function change_image(lang) {
	params = 'lang=' + lang;
	xmlHttp.open("POST", '/images_changer.php', false);
	xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
	xmlHttp.send(params);
	
	if (xmlHttp.readyState == 4) {
		if (xmlHttp.status == 200) {
			xmlResponse = xmlHttp.responseText;
			document.getElementById('big_img_container').innerHTML = xmlResponse;
		}
	}
	
	setTimeout('change_image(' + lang + ')', 5000);
}