How to return data from PHP to a jQuery ajax call

It's an argument passed to your success function:

$.ajax({
  type: "POST",
  url: "somescript.php",
  datatype: "html",
  data: dataString,
  success: function(data) {
    alert(data);
    }
});

The full signature is success(data, textStatus, XMLHttpRequest), but you can use just he first argument if it's a simple string coming back. As always, see the docs for a full explanation :)

I figured it out. Need to use echo in PHP instead of return.

<?php 
  $output = some_function();
  echo $output;
?> 

And the jQ:

success: function(data) {
  doSomething(data);
}