Como obter o id do elemento na variável PHP

<?php 
  // Place this at the top of your file
  if (isset($_POST['id'])) {
    $newID = $_POST['id'];  // You need to sanitize this before using in a query

    // Perform some db queries, etc here

    // Format a desired response (text, html, etc)
    $response = 'Format a response here';

    // This will return your formatted response to the $.post() call in jQuery 
    return print_r($response);
  }
?>

<script type='text/javascript'>
  $(document).ready(function() {
    $('.myElement').click(function() {
      $.post(location.href, { id: $(this).attr('id') }, function(response) {
        // Inserts your chosen response into the page in 'response-content' DIV
        $('#response-content').html(response); // Can also use .text(), .append(), etc
      });
    });
  });
</script>

<span id="1" class="myElement"></span>
<span id="2" class="myElement"></span>

<div id='response-content'></div>