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Undefined index in php when getting value passed from AJAX

I'm trying to get the value that I passed in AJAX to PHP. It shows an alert that says, "Success!" however it when I try to display the value in PHP, it says undefined index. Also I am passing it in the same page.
Whenever I click a button, it opens a modal and I also passing values from that button to the modal. This is evident in my JS code.
<script>
$(document).ready(function(){
$('#editModal').on('show.bs.modal', function (e) {
var id = $(e.relatedTarget).data('id'); //im trying to pass this value to php, e.g. 5
var time = $(e.relatedTarget).data('time');
var name = $(e.relatedTarget).data('name');
var stat = $(e.relatedTarget).data('stat');
var desc = $(e.relatedTarget).data('desc');
alert(id);
$("#task_id_edit").val(id);
$("#new-taskID").val(id);
$("#allotted_time_edit").val(time);
$("#task_name_edit").val(name);
$("#task_status_edit").val(stat);
$("#task_desc_edit").val(desc);
$("#task_id_ref2").val(id);
//AJAX CODE HERE
$(function() {
$.ajax({
type: "POST",
url: 'tasks.php?id='<?php $id = isset($_GET['id']) ? $_GET['id'] : ""; echo $id; ?>,
data: { "userID" : id },
success: function(data)
{
alert("success!"); //this display
}
});
});
}); // line 1131
});
</script>
PHP CODE:
<?php
$uid = $_POST['userID'];
echo $uid." is the value";
?>
It keeps getting an error that says, undefined index: userID. I am confused. Please help me how to fix this. Your help will be much appreciated! Thank you!

Echo the number in the javascript string.
Currently you will get:
url:'tasks.php?id='1,
The 1 should be concatenated or inside the quote. Try:
url: 'tasks.php?id=<?php $id = isset($_GET['id']) ? $_GET['id'] : ""; echo $id; ?>',
or take that parameter out since it doesn't appear to be being used.

Just put the $_POST['userID'] in a if statement
Undefined index: UserID is not a error it is a warning
<?php
if(isset($_POST['userID'])
{
$uid = $_POST['userID'];
echo $uid." is the value";
}
else
{
echo "Sorry Value cant be printed";
}
?>

Wordpress plugin ajax returns 0

I'm trying to send AJAX data to my wordpress table but all I can get from my PHP is a 0. Its on the admin side. Can anyone help me?
Also all of this code is inside my plugin-admin.php file inside my plugin folder.
<?php
if ( ! defined( 'ABSPATH' ) || ! current_user_can( 'manage_options' ) ) exit;
global $wpdb;
global $wp_version;
$results = $wpdb -> get_results(
"
SELECT ID, post_title, post_excerpt
FROM $wpdb->posts
WHERE post_type = 'post' and post_status NOT LIKE 'auto-draft'
AND post_title NOT LIKE 'Auto Draft'
AND post_status = 'publish'
ORDER BY post_title
"
);
add_action( 'wp_ajax_featured_submit_action', 'featured_submit_callback' );
function featured_submit_callback(){
echo "hi";
wp_die();
}
?>
<div class="wrap">
<h2>Select Posts</h2>
<select id="selected-posts" multiple="multiple">
<?php
foreach ( $results as $result ){
?><option value="<?php echo $result->ID; ?>"> <?php echo $result->post_title; ?> </option> <?php
}
?>
</select>
<br>
<input type="submit" id="sposts-submit"></input>
</div>
<script>
jQuery(document).ready(function($) {
var spostsarray = new Array();
//Click button
$("#sposts-submit").click(function(){
var spostsarray = new Array();
$("#selected-posts").each(function(item){
spostsarray.push( $(this).val() );
});
console.log(spostsarray);
var data = {
"action": "featured_submit_action",
"posts": spostsarray
}
$.ajax({
url: "<?php echo admin_url('admin-ajax.php'); ?>",
type: "POST",
action: "featured_submit_action",
data: {"posts": spostsarray},
success: function(data){
console.log(data);
}
});
});
});
</script>
I've condensed it a bit but the general idea is that I can grab all the recent posts and the user can select which ones they want to feature, send that to the PHP method and edit the table with it.
The problem is with my AJAX callback I only ever return 0 and not the data sent from the javascript.
SOLVED:
After some help from Rohil_PHPBeginner I figured it out. The reason it didn't work is that I was executing the code from the menu page at at that point it was too late to add a hook. Here is the page I used to solve it:
AJAX in WP Plugin returns 0 always

Below code worked perfectly fine for me:
<?php
global $wpdb;
global $wp_version;
$results = $wpdb -> get_results(
"
SELECT ID, post_title, post_excerpt
FROM $wpdb->posts
WHERE post_type = 'post' and post_status NOT LIKE 'auto-draft'
AND post_title NOT LIKE 'Auto Draft'
AND post_status = 'publish'
ORDER BY post_title
"
);
?>
<div class="wrap">
<h2>Select Posts</h2>
<select id="selected-posts" multiple="multiple">
<?php
foreach ( $results as $result ){
?><option value="<?php echo $result->ID; ?>"> <?php echo $result->post_title; ?> </option> <?php
}
?>
</select>
<br>
<input type="submit" id="sposts-submit"></input>
</div>
<?php
add_action( 'wp_ajax_featured_submit_action', 'featured_submit_callback' );
add_action( 'wp_ajax_nopriv_featured_submit_action', 'featured_submit_callback' );
function featured_submit_callback(){
echo "hi";
wp_die();
}
?>
<script>
jQuery(document).ready(function($) {
//Click button
$("#sposts-submit").click(function(){
var spostsarray = new Array();
$("#selected-posts").each(function(item){
spostsarray.push( $(this).val() );
});
console.log(spostsarray);
var data = {
"action": "featured_submit_action",
"posts": spostsarray
}
$.ajax({
url: ajaxurl,
type: "POST",
data: data,
success: function(data){
console.log(data);
}
});
});
});
</script>
You don't need to pass the AJAX url in that way because when I used your code, it is showing me with PHP. WordPress provides a default url for AJAX so you can use that( ajaxurl which I used in below code).
Other than that You have not added code for no-privilege user (if it is going to use only for privileged user then it is okay otherwise you need to add code for that).

WordPress returns 0 when an ajax call doesn't find a valid callback function (though the 0 could be return from many other things).
WordPress looks for callbacks matching wp_ajax_{callback} when a user is logged in and wp_ajax_nopriv_{callback} when the user is logged out. {callback} is populated with the POST'd value of the "action" hidden input. Note that you're not passing the action into your AJAX call. You should change:
data: {"posts": spostsarray},
to
data: data
Since you're not going to match a callback function without passing in action, WordPress is returning 0

x-editable post value is undefined

I just created an x-editable form :
<a href='#' class='username'
data-pk='<?php echo $key['idca']; ?>'
data-type="text"
data-placement="right"> <?php echo $key['categoryname']; ?> </a>
Then I created Javascript function to handle x-editable form :
$.fn.editable.defaults.success = function() { $(this).show() };
$.fn.editable.defaults.mode = 'inline';
$('.username').editable({
url:'edit.php',
pk:'1',
type:'text',
send:'always',
ajaxOptions:{
dataType:'json'
},
success: function(response, newValue) {
window.alert('oke');
},
error: function(response, newValue) {
window.alert('failed');
}
});
and in PHP I just create as follow :
<?php
$pk = $_POST['pk'];
$val = $_POST['value'];
$name = $_POST['name'];
print_r($_POST);
?>
But why I received message "undefined index pk, value, name" on window alert, which means I failed posting pk, value, name from x-editable..
Need helps, thank you very much

Given the following HTML
<a href="#" class="username"
data-pk="<?php echo $key['idca']; ?>"
data-type="text"
data-placement="right"
>
<?php echo $key['categoryname']; ?>
</a>
You can use this jQuery:
$.fn.editable.defaults.success = function() { $(this).show() };
$('#username').editable({
type: 'text', // optionnal if you've set up the data-type attribute
pk: $(this).data('pk'), // optionnal if you've set up the data-pk attribute
url: 'edit.php', // mandatory
title: 'Enter username'
});
This should work as per the documentation. There is no need for you to do the $.ajax({}); by yourself.

A little late but on php side when you response you should use json_encode because x-editable is expecting you to return with json string.
$pk = $_POST['pk'];
$val = $_POST['value'];
$name = $_POST['name'];
echo json_encode($_POST);
die();

AJAX- getting a specific array value in post

Im making a like system and am encorporating ajax to make it smooth. Everything works okay except it always defaults to the last post in for loop. My thinking is there is no way for the javascript to know which element of id "like" to post to.
main.js:
$(".like>a").click(function() {
$.post(base_url + "index.php/userprofile/like_post/", { post : post }, function(data) {
alert('liked');
}, "json");
return false;
});
Im passing through the post variable from the view file. I grab the postID of each post.
userprofile_view.php:
<?php foreach ($posts as $post)
{ ?>
<?php $postID = $this->model_posts->getPostData('id', $post->post); ?>
<script type="text/javascript">
var post = "<?php echo $postID; ?>";
var base_url = "<?php echo base_url(); ?>";
</script>
model_posts.php:
function likePost($post) {
$data['user_ID'] = $this->session->userdata('id');
$data['post_liked'] = $post;
$insert = $this->db->insert('user_post_likes', $data);
return $insert;
}
userprofile.php(controller):
public function like_post() {
$this->load->model('model_posts');
$post = $this->input->post('post');
$this->model_posts->likePost($post);
}
If someone couldhelp me out that would be great!

The problem is your usage of a global variable in a loop, so the variable will have only the last value of the loop.
You can use a data-* attribute like
<script type="text/javascript">
var base_url = "<?php echo base_url(); ?>";
</script>
<?php foreach ($posts as $post)
{ ?>
<?php $postID = $this->model_posts->getPostData('id', $post->post); ?>
<div class='posts'>
<div class='posts_img'>
<img src="<?php echo base_url() . 'img/profilepictures/thumbs/' . $profilepicture?>">
</div>
<div class='posts_user'>
<strong><?php echo $prefname; ?></strong>
</div>
<div class='posts_date'>
<?php echo $this->model_posts->getPostTime($post->post); ?>
</div>
<div class='post'>
<p><?php echo $post->post ?></p>
</div>
<?php if($this->model_posts->doesUserLike($me, $postID)) { ?>
<div class='unlike'>
<?php echo anchor('userprofile/unlike_post/' . $me . '/' . $postID, 'unlike'); ?>
</div>
<?php } else { ?>
<div class='like' data-post="<?php echo $postID; ?>">
<?php echo anchor('#', 'like', array('id' => 'like')); ?>
</div>
<?php } ?>
then
$(".like>a").click(function () {
var post = $(this).parent().attr('data-post');
$.post(base_url + "index.php/userprofile/like_post/", {
post: post
}, function (data) {
alert('liked');
}, "json");
return false;
});

if you're sending same ID field with different values stop, send unique IDs with selected values OR send ID with values as post array, PHP can deal with it

<script type="text/javascript">
var post = "<?php echo $postID; ?>";
var base_url = "<?php echo base_url(); ?>";
</script>
This is your problem. You're declaring these variables in global scope. So every time your PHP foreach loop iterates, you're redefining the variable in global scope, overwriting the previous value.
Instead, set an id attribute on each <a> tag to be the $postID, and get that ID in your click handler, like so:
$(".like>a").click(function() {
var post = this.id;
$.post(base_url + "index.php/userprofile/like_post/", { post : post }, function(data) {
alert('liked');
}, "json");
return false;
});
You would have to modify the code that creates the <a> tags to include the id attribute with the $postID value assigned to it...I don't see that part included in your code samples.

<input> calling a PHP function using AJAX

I am trying to call a PHP function using AJAX to check if the pressed button is the right button.
But I can't seem to figure it out.
I am using this as <input> code :
<?php
$i=0;
while ($i<4){
?>
<input style="background-color: <?php echo $buttonColors[$i]; ?>" onclick="echoHello(<?php echo $i?>)" type="submit" value="<?php echo $buttonName[$i]; ?>">
<?php $i=$i+1; } ?>
and I'm trying to call a PHP function when the button is clicked. I tried this :
<script>
function echoHello()
{
alert("<?php hello(); ?>");
}
</script>
<?php
function hello() {
echo "Hello World";
}
?>
This worked so I tried to change this to :
<script>
function echoHello(num)
{
alert("<?php hello(num); ?>");
}
</script>
<?php
function hello($num) {
if($num == 1) {
echo "Correct button!!!";
} else {
echo "WRONG BUTTON";
}
?>
But this didn't seem to work. What am I doing wrong?

I think you have quite some thing mixed up here.
I would suggest just writing out the buttons, and pass the buttons value to the javascript:
<?php
$i=0;
while ($i<4){
?>
<input onclick="echoHello(this.value)" type="submit" value="<?php echo $buttonName[$i]; ?>">
<?php
$i=$i+1;
} ?>
and then in your javascript (after adding all the jQuery goodness):
function echoHello(btnValue) {
$.ajax({
type: "POST",
url: "formhandler.php",
data: { buttonValue: btnValue }
})
.done(function( msg ) {
alert( "Data Saved: " + msg );
});
}
The javascript above will send the button value to your 'formhandler.php' page, using AJAX.
In the 'formhandler.php', you could then check what the value of $_POST["buttonValue"] is.
Using your setup, together with jQuery, PHP and JSON, it could be something like this:
function echoHello(btnValue) {
$.getJSON('page.php', {
choice: btnValue
})
.done(function(data) {
// based on $_GET["choice"], your PHP could render some JSON like:
// {"background":"image.jpg","fields":["newValue1", "newValue2", "newValue3"]}
// clear the current html
$("#form").html('');
// load a new background
$('body').css({'background-image':data.background})
// set up the new fields:
$.each(data.fields, function( i, item ) {
$("#form").append('<input type="text" value="' + item + '"/>');
});
});
}
This is just a sample, to give you an idea! It's untested also ;)