require(["dojo/_base/xhr"],

 function(xhr) {

  // Execute a HTTP GET request

  xhr.get({

      // The URL to request

      url: "get-message.php",

      // The method that handles the request's successful result

      // Handle the response any way you'd like!

      load: function(result) {

         alert("The message is: " + result);

      }

  });

});