We Keep Coding

Using AJAX to execute a PHP script through a JavaScript function

I have an anchor link with no destination, but it does have an onClick event:
<li><a href onClick='deletePost()'> Delete </a> </li>
I understand that I cannot directly execure PHP code blocks in JavaScript due to the nature of PHP and it being a server side language, so I have to utilize AJAX to do so.
When the delete link is clicked, I need it to execute this query (del_post.php)
<?php include("connect.php");
$delete_query = mysqli_query ($connect, "DELETE FROM user_thoughts WHERE id = 'id' ");
?>
I have tried to understand AJAX using similar past questions, but due to being relatively new, I cannot completely grasp it's language. Here is what I have tried:
function deletePost() {
xmlhttp=new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200){
xmlhttp.open("GET", "del_post.php", false);
xmlhttp.send();
}
}
}
But clicking the link just changes the URL to http://localhost/.

I believe the (main) problem is your empty "href" attribute. Remove that, or change it to href="#" or old school href="javascript:void()" (just remove it, imo).
It's been a while since I used XMLHttpRequest and not something like jQuery's .ajax, but I think you need to do it like so (mostly you need to .open/send before you watch for the state change):
var xmlHttpReq = new XMLHttpRequest();
if (xmlHttpReq) {
xmlHttpReq.open('GET', 'your-uri-here.php', true/false);
xmlHttpReq.onreadystatechange = function () {
if (xmlHttpReq.readyState == 4 && xmlHttpReq.status == 200) {
console.log('success! delete the post out of the DOM or some other response');
}
else {
console.log('there was a problem');
}
}
xmlHttpReq.send();
}

Can you please provide your : del_post.php file?
Normally you can show a text or alert in a
<div id="yourname"></div>
by using callback in an AJAX request :
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
document.getElementById("yourname").innerHTML = xmlhttp.responseText;
}
This response is coming from your PHP file for example :
function remove_record(ARG){
if ($condition==true)
echo "TRUE";
else
echo "FALSE";
}

You should remove href attribute from anchor tag and style the element with CSS.
Also, your script should look like this:
<script>
function deletePost() {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (xhttp.readyState == 4 && xhttp.status == 200) {
// Do something if Ajax request was successful
}
};
xhttp.open("GET", "del_post.php", true);
xhttp.send();
}
</script>

You are trying to make the http request inside the callback.
You just need to move it outside:
function deletePost() {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
alert(xmlhttp.responseText);
}
}
xmlhttp.open("GET", "del_post.php", false);
xmlhttp.send();
}
Removing the href attribute will prevent the refresh. I believe that is valid in HTML5.

Ok... I'm just a hobbyist, so please forgive me any inaccuracies in the typing but this works: A format I use for an ajax call in an <a> element is:
<a href="javascript:" onclick="functionThatReallyCallsAjax()">
So that I have more flexibility(in case I need to check something before I send the ajax). Now, for an ajax call you need:
What file to call
What to do with the response from the file you called
What to do if an I/O error happens
So we have this function - not mine, leeched amongst thousands from somewhere - probably here :) - and probably well known, my apologies to the author, he is a genius: This is what you call for the ajax thing, where 'url' is the file you want to 'ajax', 'success' is the name of the function that deals with results and error is the name of the function that deals with IO errors.
function doAjaxThing(url, success, error) {
var req = false;
try{
// most browsers
req = new XMLHttpRequest();
} catch (e){
// IE
try{
req = new ActiveXObject("Msxml2.XMLHTTP");
} catch(e) {
// try an older version
try{
req = new ActiveXObject("Microsoft.XMLHTTP");
} catch(e) {
return false;
}
}
}
if (!req) return false;
if (typeof success != 'function') success = function () {};
if (typeof error!= 'function') error = function () {};
req.onreadystatechange = function(){
if(req.readyState == 4) {
return req.status === 200 ?
success(req.responseText) : error(req.status);
}
}
req.open("GET", url, true);
req.send(null);
return req;
}
You will naturally need to include the success+error functions:
function dealWithResponse(textFromURL)
{
//textFromURL is whatever, say, a PHP you called in the URL would 'echo'
}
function ohNo()
{
//stuff like URL not found, etc.
alert("I/O error");
}
And now that you're armed with that, this is how you compose the real call inside the function you called at the <a>:
function functionThatReallyCallsAjax()
{
//there are probably many scenarios but by having this extra function,
//you can perform any processing you might need before the call
doAjaxThing("serverFile.php",dealWithResponse,ohNo);
}
One scenario might be when you need to pass a variable to the PHP you didn't have before. In this case, the call would become:
doAjaxThing("serverFile.php?parameter1=dogsRock",dealWithResponse,ohNo);
And now not only you have PHP sending stuff to JS, you have JS sending to PHP too. Weeeee...
Final words: ajax is not a language, its a javascript 'trick'. You don't need to fully understand what the first 'doAjaxThing' function does to use this, just make sure you are calling it properly. It will automatically 'call' the 'deal WithResponse' function once the response from the server arrives. Notice that you can continue doing your business (asynchronous - process not time-tied) till the response arrives - which is when the 'deal WithResponse' gets triggered -, as opposed to having a page stop and wait (synchronous - time tied) until a response arrives. That is the magic of ajax (Asynchronous JAvascript and Xml).
In your case you want to add the echo("success") - or error! - in the PHP, so that the function 'dealWithResponse' knows what to do based on that info.
That's all I know about ajax. Hope this helps :)

how to fix startWith not working in chrome

I am checking some date whether available or not from DB using Ajax using below my code,
var url = "ValidateDateFromDB.jsp?cdate="+selecteddate.value;
if (window.XMLHttpRequest)
req = new XMLHttpRequest();
else if (window.ActiveXObject)
req = new ActiveXObject("Microsoft.XMLHTTP");
req.open("GET", url, true);
req.onreadystatechange =callback;
req.send(null);
function callback()
{
if (req.readyState == 4)
{
if (req.status == 200)
{
var message = req.responseText;
alert(message);
if(message.startsWith("Available"))
{
alert("Availabe");
}
else
{
alert("Not Availabe");
}
}
}
}
I am getting output like below image,
It is working fine in firefox but not working in chrome.I checked out that startsWith works only chrome above 40 version.So to fix this i used == operation like below,
if(message=="Available")
{
alert("Availabe");
}
else
{
alert("Not Availabe");
}
But this code always goes to else part that i know why.
someone tell me how to fix this?

Ajax POST never gets sent?

I'm having an issue with my ajax POST for some reason the POST is never made! can't for the life of me work it out?
yeah so I used the network debug tool in firefox to check the POST request but the POST request never gets made..
The function is definitely getting called too as I have added an alert alert("start") to the beginning of the function which does run.
AJAX
<script>
function updateContentNow(pid2, status2) {
var mypostrequest = new ajaxRequest();
mypostrequest.onreadystatechange = function() {
if (mypostrequest.readyState == 4) {
if (mypostrequest.status == 200 || window.location.href.indexOf("http") == -1) {
document.getElementById("livestats").innerHTML = mypostrequest.responseText;
} else {
alert("An error has occured making the request");
}
}
}
var parameters = "cid=clientid&pid=6&statusinfo=approve";
mypostrequest.open("POST", "http://mydomain.com.au/content-approval/ajax.php", true);
mypostrequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
mypostrequest.send(parameters);
}
</script>
UPDATED WORKING: thanks peps..
<script>
function updateContentNow(pid2,status2)
{
var mypostrequest=new XMLHttpRequest()
mypostrequest.onreadystatechange=function(){
if (mypostrequest.readyState==4){
if (mypostrequest.status==200 || window.location.href.indexOf("http")==-1){
document.getElementById("livestats").innerHTML=mypostrequest.responseText;
}
else{
alert("An error has occured making the request");
}
}
}
var parameters="cid=<?=$clientID?>&pid="+pid2+"&statusinfo="+status2;
mypostrequest.open("POST", "http://mydomain.com.au/content-approval/ajax.php", true);
mypostrequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
mypostrequest.send(parameters);
}
</script>

Are you using some external Ajax classes, at least ajaxRequest() object doesn't exist in plain JavaScript. Try to substitute this line
var mypostrequest = new ajaxRequest();
by that:
var mypostrequest=new XMLHttpRequest();
Then even calling your method with
updateContentNow("","");
at least makes the POST request as you easily can see with Firebug.

AJAX - JSP not executed on POST

I need to send a mail with jsp, but the page itself mustn't reload. The whole implementation is working fine when reloading on the POST-event, but adjusting the code to work with ajax breaks it. It seems that the jsp-Code within the index.jsp is not executed, when the ajax event is triggerd.
I am gonna show some snippets:
index.jsp
<%
String result = "=(";
String to = request.getParameter("rec_mail");
if(to != null) {
String from = request.getParameter("sendermail");
String host = "mailserver";
Properties properties = System.getProperties();
properties.setProperty("mail.smtp.host", host);
Session mailSession = Session.getDefaultInstance(properties);
try{
MimeMessage message = new MimeMessage(mailSession);
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO,
new InternetAddress(to));
message.setSubject("Feedback");
message.setText(request.getParameter("feedbackinput"));
Transport.send(message);
result = "Sucess!";
}catch (MessagingException e) {
e.printStackTrace();
result = "failed!";
}
}
out.println(request.getParameter("sendermail"));
out.println(result);
%>
<input id="bsend" class="fbutton" type="submit" name="send" value="Send" onclick="loadContent()" style="float:right; width:18%; height:35%;" >
ajax.js
var xmlhttp
function loadContent() {
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Your browser does not support Ajax!");
return;
}
var url="./index.jsp";
xmlhttp.open("post",url,true);
xmlhttp.send(null);
xmlhttp.onreadystatechange=getOutput;
}
function getOutput()
{
if (xmlhttp.readyState==4)
{
alert("Message sent!");
}
}
function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
return new ActiveXObject("Microsoft.XMLHTTP");
}
return null;
}
(just showing the relevant parts, everywhere)
I get the alert-message, but no mail is sent ... I hope it is clear, what I am trying to do..
Thank you!
Best regards

Don't you also need to set a header for a HTTP Post
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
also, not sure if it will make a difference but I would make "post" to "POST".

jsp with ajax two simultaneous requests only getting one response

I have a jsp page where I'm trying to send multiple (two currently) ajax requests at once, but I only seem to get the second response. This guy described my problem exactly, but his solution didn't work for me.
Here is my js code:
function createRequestObject(){
var req;
if(window.XMLHttpRequest){
//For Firefox, Safari, Opera
req = new XMLHttpRequest();
} else if(window.ActiveXObject){
req = new ActiveXObject("Microsoft.XMLHTTP");
}
else{
//Error for an old browser
alert('Browser error');
}
return req;
}
function sendRequest(method, url, d){
var http = createRequestObject();
var div = d;
if(method == 'get' || method == 'GET'){
http.open(method, url, true);
http.onreadystatechange = function() {
if(http.readyState == 4 && http.status == 200){
var response = http.responseText;
if(response){
document.getElementById(div).innerHTML = response;
}
}
};
http.send(null);
}
}
And here is how I call that code:
QC1 Status: <div id='qc1'>blah</div>
<br />UAT2 Status: <div id='uat2'>blah2</div>
<a onclick="sendRequest('GET','index.jsp?qc1.properties=true','qc1'); " href="#">qc1</a>
<a onclick="sendRequest('GET','index.jsp?uat2.properties=true','uat2'); " href="#">uat2</a>
<a onclick="sendRequest('GET','index.jsp?qc1.properties=true','qc1'); sendRequest('GET','index.jsp?uat2.properties=true','uat2'); " href="#">both</a>
When I call one at a time they work as expected, but the "both" link only updates with the second request, even though I know it runs the index.jsp code for both.
EDIT: Ok, after fixing the obvious mistake that BalusC pointed out, it works. Fixed it in this post too.

You're indeed sending two requests on the same URL and updating the same div. Shouldn't the first one go to the qc1 one and update the qc1 one?