Using the post method on polymer

[105...@students.wits.ac.za]

Hie. So i'm new to polymer and I've been having problem when posting. It returns a null even though the php file returns something. The GET method works fine though. Here is my code:

The compent:

<template>
   <button type="submit" onclick="getPost" class="btn btn-default" id="register-form" style="margin-left: 35%; background-color: #008000; color: black; width: 30%;">Submit</button>
   <iron-ajax
        id="ajax"
        method="POST"
        body='[{"id": "1"}]'
        url ="http://localhost/api/post.php"
        on-response="success"
        lastError="error"
        debounce-duration="3000">
    </iron-ajax>
</template>
<script>
    Polymer({
      is: 'register-form',
      getPost:function(){
        this.$.ajax.generateRequest();
      },
      success:function(r){
        alert(r.detail.response);
      },
      error:function(r){
        alert(r.detail.response);
      }
    });
</script>

Enter code here...

The php:

<?php
    header('Access-Control-Allow-Origin: *');
    if ($_POST){
        echo $_POST['id'];
    }
?>

 
Initially I wanted the the php to return a json but it kept on returning null.So i decided to change it to that to see if it will return the id I posted but it still returned null. I've tried the solutions i found on the Internet but it still dint work.Please help.