$.ajax POST Undefined index - php

Question

Apologies in advance for any mistakes. This is my first post on StackOverflow.
So basically I have a php function. Inside it is a jQuery click function with a variable, into which I'm saving the clicked element's text. I'm trying to send that variable's value to my Uredi.php file, via $.ajax function, to save it into a php variable. However, I'm getting an "Undefined index" error. Help would be greatly appreciated. Thank you.
Here's the code:
PHP function:
public function uredi()
{
?>
<script>
$('.edit').click(function(){
$('.naslov_edit').val($(this).text());
$('#on_top').hide();
var refId = $(this).text();
$.ajax({
url: 'uredi.php',
type: "POST",
data: {id: refId},
success: function(data){
alert(data);
}
});
});
</script>
<?php
}
Uredi.php:
<?php
include 'Funkcije.php';
$uredi = new urejanje();
$uredi->uredi();
$id = $_POST['id'];
echo $id;
?>
Funkcije.php is the file with the uredi() function.
EDIT: Thank you everyone for helping. I figured out the problem. Turns out I just had to clean up my code a bit.

Answer 1

Why are you assigning $(this).text() to var id and then not using it in the $.ajax()? Remember scope and what doe $(this) actually reference within the $ajax()? I would also shy away from naming variables "id" Try:
var refId = $(this).text();
$.ajax({
url: 'uredi.php',
type: "POST",
//dataType: 'json',
data: {id: refId},
success: function(data){
alert(data);
}
});

Answer 2

Use this;
$.ajax({
url: 'uredi.php',
type: "POST",
data: "id=" + refId,
success: function(data){
alert(data);
}
});

Answer 3

perhaps you meant to read the post vars before initializing the class and maybe even pass Id in?
$id = $_POST['id'];
$uredi = new urejanje();
$uredi->uredi($id);
In any case I think You'll need to show us whats inside Funkcije.php