// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();

// creates an XMLHttpRequest instance
function createXmlHttpRequestObject() 
{
  // will store the reference to the XMLHttpRequest object
  var xmlHttp;
  // this should work for all browsers except IE6 and older
  try
  {
    // try to create XMLHttpRequest object
    xmlHttp = new XMLHttpRequest();
  }
  catch(e)
  {
    // assume IE6 or older
    var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
                                    "MSXML2.XMLHTTP.5.0",
                                    "MSXML2.XMLHTTP.4.0",
                                    "MSXML2.XMLHTTP.3.0",
                                    "MSXML2.XMLHTTP",
                                    "Microsoft.XMLHTTP");
    // try every prog id until one works
    for (var i=0; i<XmlHttpVersions.length && !xmlHttp; i++) 
    {
      try 
      { 
        // try to create XMLHttpRequest object
        xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
      } 
      catch (e) {}
    }
  }
  // return the created object or display an error message
  if (!xmlHttp)
    alert("Error creating the XMLHttpRequest object.");
  else 
    return xmlHttp;
}

var cache = new Array();
// called to read a file from the server
function changeClassPID(pid,tab)
{
  cache.push("pid="+pid+"&tab="+tab);
  // only continue if xmlHttp isn't void
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // try to connect to the server
   try
    {	  
	  var cacheEntry = cache.shift();
      // initiate reading the async.txt file from the server
      xmlHttp.open("POST", "ajax/changeClassPID.php", false);
	  xmlHttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
      xmlHttp.onreadystatechange = handleRequestStateChange;
      xmlHttp.send(cacheEntry);
    }
    // display the error in case of failure
    catch (e)
 
    {
      alert("Can't connect to server:\n" + e.toString());
    }
  }
}

function getPetNameByCode(code)
{
  cache.push("code="+code);
  // only continue if xmlHttp isn't void
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // try to connect to the server
   try
    {	  
	  var cacheEntry = cache.shift();
      // initiate reading the async.txt file from the server
      xmlHttp.open("POST", "ajax/getPetNameByCode.php", false);
	  xmlHttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
      xmlHttp.onreadystatechange = handleRequestStateChange;
      xmlHttp.send(cacheEntry);
    }
    // display the error in case of failure
    catch (e)
    {
      alert("Can't connect to server:\n" + e.toString());
    }
  }
}

function checkRepeatData(value, rsid, field, tab, dataid)
{
  cache.push("value="+value+"&rsid="+rsid+"&field="+field+"&tab="+tab+"&dataid="+dataid);
  // only continue if xmlHttp isn't void
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // try to connect to the server
   try
    {	  
	  var cacheEntry = cache.shift();
      // initiate reading the async.txt file from the server
      xmlHttp.open("POST", "ajax/checkRepeatData.php", true);
	  xmlHttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
      xmlHttp.onreadystatechange = handleRequestStateChange;
      xmlHttp.send(cacheEntry);
    }
    // display the error in case of failure
    catch (e)
 
    {
      alert("Can't connect to server:\n" + e.toString());
    }
  }
}

function updateMemberData(field, value)
{
  cache.push("value="+value+"&field="+field);
  // only continue if xmlHttp isn't void
  if (xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
  {
    // try to connect to the server
   try
    {	  
	  var cacheEntry = cache.shift();
      // initiate reading the async.txt file from the server
      xmlHttp.open("POST", "ajax/updateMemberData.php", true);
	  xmlHttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
      xmlHttp.onreadystatechange = handleRequestStateChange;
      xmlHttp.send(cacheEntry);
    }
    // display the error in case of failure
    catch (e)
    {
      alert("Can't connect to server:\n" + e.toString());
    }
  }
}

// function that handles the HTTP response
function handleRequestStateChange() 
{
if (xmlHttp.readyState == 4) 
  {
    // continue only if HTTP status is "OK"
    if (xmlHttp.status == 200) 
    {
      try
      {
        response = xmlHttp.responseText;
        eval(response);
      }
      catch(e)
      {
        alert("Error reading the response: " + e.toString());
      }
    } 
    else
    {
      // display status message
      alert("There was a problem retrieving the data:\n" + 
            xmlHttp.statusText);
    }
  }
}