使用jquery将Php变量发送到php脚本

I am trying to send a variable with jquery to a php script now this is my first try after reading the documentation but it wont work. can anyone give me some advice ? I didn't realize the error in code. The variable I want to send is $id. I defined it with '1'

<?php
$id = '1';
?>

jquery part

<script>
$(document).ready(function() {    // Anfang Dokument Ready Funktion
$("p").click(function () {  // Anfang Klick Funktion
 var id = $(this).html();    // Inhalt in Klickfunktion
// Beginn Ajax Segment mit Angabe von Typ Url Data und Div #ausgabe
    $.ajax({
        type: 'POST',
        url: 'http://localhost/ajax.php',
        data: 'id='+id',
        success: function(data){
            $('#ausgabe').html(data);
        }
        });     // Ende Ajax Segment 
});    // Ende Klick Funktion
});  // Ende Dokument Ready Funktion
</script>

<div id="ausgabe"></div>
<p><button>Sende Variable</button></p>

The ajax.php

<?php
$id = $_POST['id'];
echo $id;
?>

The right form to send info with ajax to PHP is:

$.ajax({
        type: 'POST',
        url: 'http://localhost/ajax.php',
        data: id:id,
        success: function(data){
            $('#ausgabe').html(data);
        }
        }); 

To send by reference. If you want to send without reference just use:

$.ajax({
        type: 'POST',
        url: 'http://localhost/ajax.php',
        data: id,
        success: function(data){
            $('#ausgabe').html(data);
        }
        }); 

Rely on data-* attributes better:

HTML

<a href="#" data-id="<?php echo $id; ?>">Click me</a>

JS

$(function(){

  $('a[data-id]').click(function(event){

    event.preventDefault();

    // $(this).data('id') fetches the data-id attribute from your anchor
    $.post( someUrl, { id : $(this).data('id')} ).done(function(){ ... })

  })

})

Simple Send it like this

 $.ajax({
        type: 'POST',
        url: 'http://localhost/ajax.php',
        data: {id : <?php echo $id ?>},
        success: function(data){
            $('#ausgabe').html(data);
        }
        });     // Ende Ajax Segment