Who to append php on chnage with Jquery Ajax

Question

I am trying to append php script to the dom in a div that has the class .new-session but it doesn't work how it should.

Here is my code

$('select[name=quantity]').change(function() {
  quantity = $(this).val();

  if (quantity == 20) {
    newSession = '<?php echo $_SESSION[\'product\'][\'quantity\'] = 20; ?>';
  }
  elseif(quantity == 30) {
    newSession = '<?php echo $_SESSION[\'product\'][\'quantity\'] = 30; ?>';
  }
  elseif(quantity == 40) {
    newSession = '<?php echo $_SESSION[\'product\'][\'quantity\'] = 40; ?>';
  }
  elseif(quantity == 50) {
    newSession = '<?php echo $_SESSION[\'product\'][\'quantity\'] = 50; ?>';
  }
  elseif(quantity == 60) {
    newSession = '<?php echo $_SESSION[\'product\'][\'quantity\'] = 60; ?>';
  }

  $.ajax({
    url: "/multisite/",
    dataType: "html",
    success: function(newSession) {
      $('.set-session').append(newSession);
    }
  })

});

<div class="set-session">

</div>

Answer 1

You can't append PHP to the DOM, PHP code is run on the server when the page is being created. You use AJAX to run server code in response to a user action, and the script that receives the AJAX call updates the session.

Here's how you can do what you want:

$('select[name=quantity]').change(function() {
    var quantity = $(this).val();
    $.ajax({
        url: "/multisite/setquantity.php",
        data: { quantity: quantity }
    });
});

The PHP in setquantyt.php should be like:

<?php
session_start();
$_SESSION['product']['quantity'] = intval($_GET['quantity']);