//Gets the browser specific XmlHttpRequest Object 
function getXmlHttpRequestObject() {
 if (window.XMLHttpRequest) {
    return new XMLHttpRequest(); //Mozilla, Safari ...
 } else if (window.ActiveXObject) {
    return new ActiveXObject("Microsoft.XMLHTTP"); //IE
 } else {
    //Display our error message
    alert("Your browser doesn't support the XmlHttpRequest object.");
 }
}
 
//Our XmlHttpRequest object
var receiveReq = getXmlHttpRequestObject();
var URI = "";
//Initiate the AJAX request
function makeRequest(url, params) {
//If our readystate is either not started or finished, initiate a new request
 if (receiveReq.readyState == 4 || receiveReq.readyState == 0) {
   //Set up the connection to captcha_test.html. 
   //True sets the request to asyncronous(default) 

   receiveReq.open("POST", url, true);
   //Set the function that will be called 
   //when the XmlHttpRequest objects state changes
   receiveReq.onreadystatechange = updatePage; 
 
   receiveReq.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
   receiveReq.setRequestHeader("Content-length", params.length);
   receiveReq.setRequestHeader("Connection", "close");
 
   //Make the request
   receiveReq.send(params);
 }   
}
 
//Called every time our XmlHttpRequest objects state changes
function updatePage() {
 //Check if our response is ready
 if (receiveReq.readyState == 4) {
   if(receiveReq.status == 200){
	 // khong co loi xay ra
     if(receiveReq.responseText == "0"){
		window.location = URI;
	 }
	 else{
		 document.getElementById("commentDetails").innerHTML = "<font color='#FF0000'><strong>"+receiveReq.responseText+"</strong></font>";
	 	 document.getElementById("captchaImage").innerHTML = "<img src='http://localhost/nhv/library/creat_image.php' />";
	 }
   }
 }
}
 
//Called every time when form is perfomed
function getParam(form,uri,urlProcess) {
 //Set the URI
 URI = uri;
 //Set up the parameters of our AJAX call
 var postStr = "captcha="+encodeURIComponent( form.captcha.value )+"&tieude="+encodeURIComponent( form.tieude.value )+"&noidung="+encodeURIComponent( form.noidung.value );
 //Call the function that initiate the AJAX request
 makeRequest(urlProcess, postStr);
}