We Keep Coding

Pass javascript string variable to another page and get the variable in PHP with AJAX

I basically don't seem to understand sending a variable to another page.
I've tried PHP sessions, javascript cookies and ajax POST and GET.
I'm trying to send the innerHTML of a div, with the data created by a jQuery call,
a variable called savedartists. It displays correctly in the console.log on the sending page but the $_POST['savedArtists']
is undefined in the receiving page. I have spent hours looking at different posts on this site but I haven't been able to get it to work.
Any help is appreciated.
<input class="et_pb_button et_pb_button_0 et_pb_bg_layout_light" onClick="savequote();" type="button" id="savedchoices" value="Commander la prestation" >
<script>
function savequote() {
var savedartists = document.getElementById('selectedList').innerHTML;
console.log(savedartists);
$.ajax({
type: "POST",
url: 'example.com/artiste/mise-en-relation/',
data: { savedArtists : savedartists },
success: function(data) {
console.log("success!");
location.href = "example.com/artiste/mise-en-relation/";
}
});
}
</script>
On the receiving page (example.com/artiste/mise-en-relation/)
<?php
if(isset($_POST['savedArtists']))
{
$uid = $_POST['savedArtists'];
echo $uid;
} else {
echo 'zit!';
}
?>
Thanks for your time

Capturing as an answer for future readers...
Fundamentally what's happening here is that two requests are being made to the target page. The first one is the AJAX request:
$.ajax({
type: "POST",
url: 'example.com/artiste/mise-en-relation/',
data: { savedArtists : savedartists },
success: function(data) {
//...
}
});
This is a POST request which contains the data you expect, and works just fine. However, the result of this request is being ignored. That result is available in the success callback, but the code doesn't do anything with it:
console.log("success!");
location.href = "example.com/artiste/mise-en-relation/";
Instead, what the code is doing is performing a redirect. This creates a second request to that same page (though it's essentially irrelevant that it's the same page). This is a GET request and contains no data to send to the server.
At its simplest, you should either use AJAX or redirect the user. Currently you're mixing both.
I want to redirect to the other page.
In that case AJAX is the wrong tool for the job. You may not even need JavaScript at all, unless you want to modify the elements/values of a form before submitting that form. But if all you want is to POST data to another page while directing the user to that page, a plain old HTML form does exactly that. For example:
<form method="POST" action="example.com/artiste/mise-en-relation/">
<input type="text" name="savedArtists">
<button type="submit">Submit</button>
</form>
In this case whatever value the user enters into the <input> will be included in the POST request to example.com/artiste/mise-en-relation/ when the user submits the form.

How to make a request using jQuery to a django server to refresh infos on page

I made a website in python using Django. My site allows you to control lights while indicating if the light is on or not.
I'm looking for a solution that could make a simple request with data to the server and send data back to the client without updating the entire page but only a part of it.
My ideal would be for the client to make a request to the server with identification data. Then, the server returns the updated data that the user is allowed to have.
Is that possible to make a JavaScript to do that ? And the server, how it can return data to the client ?

You can Use jquery AJAX for send request and get a response and Update an element or part of the page you can read more about it in :
W3schools
or :
jquery.com
AJAX function I use for PHP project:(Just for example)
$.ajax({
type: "POST",
url: Url,
data: InfoData, // data if you want to send for example InfoData={dataName: variable} or you can set this = '' if you don't want to send data
datatype: "html",
success: function(result) {
console.log(result);
}
});

Why is python requests getting different results than Ajax

I am trying to write a Python script that logs into website for me and downloads my messages. I'm using the the "requests" library and succesfully able to log in with a session
The website uses js/Ajax to download the actual messages client side after the messages page has been loaded, and uses pagination to achive an infinite list of messages effect.
The messages page url is in the form of https://website.com/messages. and that page contains an Ajax call that retrives the messsages like this:
$.ajax({
url: '/messages?mailbox=' + mailbox + optional params
}).done(function(data) {
urlLazyLoading = data.next_page_url;
$.each(data, function(i, v) {
//from this point on, data for each message can be
//accessed using the v object as such:
//v.sender, v.date, v.last_message, etc
//and the <ul> element is populated with '<li>'s
But when I try to access the same url in python (after I've loggedin) as such:
session.get('https://website.com/messages?mailbox=inbox')
instead of getting a json response with the messages data, I get the same/original messages page.
the only parameter passed to ajax in the code above is url, so by defult it should be just making a simple GET request, which is what I'm doing.
Is it possible that maybe somewhere else in the code ajax is being set up to default to POST or have some other non-default settings?
or is the server somehow detecting that one request is coming from ajax and the other from sessions? maybe using user-agent?

Got it!
Ajax sends a header value by default:
{'X-Requested-With': 'XMLHttpRequest'}
I added that in and viola
headers = {'X-Requested-With': 'XMLHttpRequest'}
r = s.get("https://website.com/messages?mailbox=inbox",headers=headers)

Javascript not proceeding aynchronously beyond AJAX call

When the user presses the 'Process' button on my application, I would like the application to trigger an AJAX request and then immediately redirect the user to another screen without waiting for the results of the AJAX request. I believe I have coded it appropriately but I notice that the screen is waiting for the AJAX to finish before redirecting. Am I missing something below?
$('#process-btn').on('click', function()
{
// disable the process & cancel buttons to prevent
// double submission or interruption
$('#cancel-btn').addClass('disabled');
$(this).addClass('disabled');
// trigger the AJAX require to process the uploaded file on the server side
$.ajax({
url: $('#form').attr('action'),
type: 'post',
data: $('#form').serialize(),
success: function() {
//on success
}
});
// redirect the user to view list
// this line is not being called immediately -
// this is being called only after AJAX returns
window.location.replace( www_root + 'Home/index' );
});

Because the button you have this handler hooked to is a submit button for a form (per your comments) and you aren't preventing the default behavior of that button, then the form submit will happen immediately and when the submit returns, it will change the page regardless of what your code tries to do.
So, the issue is that the returned form submit was overcoming what your code was trying to do.
You may be living a little dangerously by redirecting before your ajax call has finished. It's possible the browser could drop the ajax connection before the TCP buffers had actually been sent as TCP often has a small delay before sending buffers in order to collect consecutive data into common packets. It would be much safer to either redirect after a short timeout or redirect on the complete event which will be called regardless of ajax success.
If you really want to do the redirect BEFORE the ajax call has completed, you can experiment with the timeout value (shown here as set to 500ms) in this code to see what works reliably in multiple browsers:
$('#process-btn').on('click', function(e) {
// prevent default form post
e.preventDefault();
// disable the process & cancel buttons to prevent
// double submission or interruption
$('#cancel-btn').addClass('disabled');
$(this).addClass('disabled');
// trigger the AJAX require to process the uploaded file on the server side
$.post($('#form').attr('action'), $('#form').serialize());
// redirect the user to view list
// this being called after a short delay to "try"
// to get the form ajax call sent, but not "wait" for the server response
setTimeout(function() {
window.location.replace( www_root + 'Home/index' );
}, 500);
});
Also, note that I've added an e.preventDefault() and added the e argument to the event handler to make sure the form is not posted by default, only by your ajax code.
And, the timeout time is set here to 500ms. What you need is enough time for the TCP infrastructure in the host computer to send all your form data before you start the redirect. I see a mention of a "file upload" in your comments. If this form is actually uploading a file, that could take way, way longer than 500ms. If it's just sending a few form fields, that should go pretty quickly assuming there are no connection hiccups.
Caveat: Doing it this way is not the 100% reliable way of getting data to your server. There can easily be some conditions where it takes longer than usual just to do a DNS lookup before connecting with your server or your server could momentarily take longer to respond to the initial connection before data can be sent to it. The only 100% reliable way is to wait until the ajax call has succeeded as mentioned elsewhere.
You could perhaps have the best of both worlds (reliability + fast response) if you changed the way your server processes the ajax call so that as soon as it has received the data, it returns a successful response (e.g. in milliseconds after receiving the data) and then after it has sent back the successful response so the browser can then reliably do its redirect, it takes it's 2-3 minutes to actually process the data. Remember, you don't gave to wait until you are done processing the request to return a response. Then, you know that the server has received the data, but the browser doesn't have to wait for the processing time. If you don't always want this ajax call to work that way, you can pass an argument to the ajax call to instruct the server whether you want the fast response or not.

Why not try this:
$.ajax({
url: $('#form').attr('action'),
type: 'post',
data: $('#form').serialize(),
success: function() {window.location.replace( www_root + 'Home/index' );}
});

Page waits for AJAX before changing location

This question might seem a bit odd, the problem arised when the page went through webtests.
The page uses an AJAX call (async set to true) to gather some data. For some reason it won't swap pages before the AJAX call has returned - consider the following code:
console.log("firing ajax call");
$.ajax({
type: "POST",
url: "requestedService",
data: mode : "requestedMethod",
cache: false,
dataType: "json",
success: function() { console.log("ajax response received") },
error: null,
complete: null,
});
console.log("changing window location");
window.location = "http://www.google.com"
The location only changes after AJAX returns the response. I have tested the call, it is in fact asynchronous, the page isn't blocked. It should just load the new page even if the AJAX call hasn't completed, but doesn't. I can see the page is trying to load, but it only happens once I get the response. Any ideas?
The console output is:
firing ajax call
changing window location
ajax response received

This seems to work fine for me. The location is changed before the code in the async handler executes. Maybe you should post some real code and not a simplified version, so that we can help better.
Here is a demonstration that works as you expect: http://jsfiddle.net/BSg9P/
$(document).ready(function() {
var result;
$("#btn").on('click', function(sender, args) {
setInterval(function() {
result = "some result";
console.log("Just returned a result");
}, 5000);
window.location = "http://www.google.com";
});
});
And here is a screenshot of the result: http://screencast.com/t/VbxMCxxyIbB
I have clicked the button 2 times, and you can see in the JS console that the message about the location change is printed before the result each time. (The error is related to CORS, if it was the same domain, it would navigate).

Bit late but maybe someone else will have the same issue.
This answer by #todd-menier might help: https://stackoverflow.com/questions/941889#answer-970843
So the issue might be server-side. For eg, if you're using PHP sessions by default the user's session will be locked while the server is processing the ajax request, so the next request to the new page won't be able to be processed by the server until the ajax has completed and released the lock. You can release the lock early if your ajax processing code doesn't need it so the next page load can happen simultaneously.