If you’re like me, you probably tried just including the php files per the learn xajax in 10 minutes docs and ended up getting some arcane error message in Firebug that reads “[Exception... "'[object Object]‘ when calling method: [nsIDOMEventListener::handleEvent]” nsresult: “0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)” location: “<unknown>” data: no] Line 0″

huh?  what am I supposed to do with that?  google turns up nothing… (which is why i’m adding it here)

hmm.. ok over to the CI docs on xajax and there’s an article ( http://codeigniter.com/wiki/XAJAX/ ) .  Perfect!

wait… what is that??  right there on the third line, that little “Note: This doc is obsolete”.  noooo!!

alright, maybe i can still pull this apart.. it kind of looks good, but it’s got a lot of what appears to be unecessary steps (like creating a library loader) and munging the view code into the controller.  i’d like to keep the view code in the view and i don’t need to be messing with library loaders.  let’s try something else:  XAJAX + CodeIgniter in 3… 2… 1…

Install XAJAX
into the funny CodeIgniter directory structure!

1. Download XAJAX Standard here: http://xajaxproject.org/en/download/ At the time of this writing, the most recent release is 0.5, but it shouldn’t matter much.
2. Unzip the zip file
3. Upload the xajax_0.5_standard/xajax_core folder to /www/system/application/xajax_0.5_standard/xajax_core
4. Upload the xajax_0.5_standard/xajax_js folder to /www/xajax_0.5_standard/xajax_js

I like to leave the version number in the folder names, otherwise, how will I remember a year from now if I need to upgrade?  Or what version to upgrade from?

Notice we had to put the xajax php code with the CI php code, and xajax looks for web stuff based on your url so we have to put it someplace web-accessible which is why we put it in our web root folder.  That’s the first tricky bit.  xajax is nice enough to pop up an error message letting you know if it can’t find the js files it needs (go xajax!  much appreciate that).  I had no need for the other xajax folders as I was just doing simple ajax requests, but i imagine that once you get this working, you can probably deduce where they might belong should a project require them.

Add XAJAX Include Paths
You don’t have to do this, but I did because I think it makes upgrading to a later version of xajax that much easier. I defined the path in a constant by creating a util directory and constants.php file at /www/system/application/util/constants.php with the following code:

<?php
define ("XAJAX_FOLDER", "xajax_0.5_standard");
define ("XAJAX_PHP", APPPATH . XAJAX_FOLDER . '/xajax_core/xajax.inc.php');

I didn’t close my php tag on purpose. You < href="http://codeigniter.com/user_guide/general/styleguide.html#php_closing_tag" target="_blank">shouldn’t close your php tags. Remember that for your next job interview.

When I upgrade xajax later, all I’ll have to do is upload the new version, and change the XAJAX_FOLDER define and not touch any code.

Add XAJAX to the Controller

Pick a controller.. any controller. You can have a special ajax controller, or I would recommend picking the controller for your view (makes sense right? a view requires ajax and its ajax requests are sent to its controller).

Add a constructor to the controller which will initialize xajax. For poipedia I have a controller class View defined in CI at controllers/view.php. The beginning of that controller looks like this:

<?php
 
require_once(APPPATH . 'util/constants.php');
 
require_once(XAJAX_PHP);
 
class View extends Controller {
 
 
	private $xajax = '';
 
    function View() {
        parent::Controller();
        $this->xajax = new xajax();
        $this->xajax->registerFunction(array('addFavorite',&$this,'addFavorite'));
        $this->xajax->processRequest();
    }
 
    function addFavorite()
    {
        // Instantiate the xajaxResponse object
        $objResponse = new xajaxResponse();
        // add a command to the response to assign the innerHTML attribute of
        // the element with id="SomeElementId" to whatever the new content is
        $objResponse->assign("lnkFav","innerHTML", 'xajax response!');
 
        //return the xajaxResponse object
        return $objResponse;
    }
 
 
 
    function poi($id)
    {
        $this->load->model('poi');
        $this->load->model('picture');
        $this->load->model('comment');
 
        $data = array('xajax' => $this->xajax,
        					   'poi' => $this->poi->getPoi($id),
						 'pictures' => $this->picture->getPicturesForPoi($id),
        				 'comments' => $this->comment->getCommentsForPoi($id));
 
        $this->load->view('poiDetail', $data);
    }

Let’s break that down. The important steps are:

We initialize xajax in the constructor of the controller, and assign the xajax object to a class variable which we’ll pass to our view later
The php function we want to call via ajax is located in our controller (in this case “addFavorite”
The $xajax class variable which was initialized by our constructor is passed to our view to be used by the view. (the first array assignment in $data in the poi function–those other things like comments and pictures you probably won’t be using on your site. )

Add XAJAX to the View

In my case the view I’m loading in the poi function is poiDetails.php at /system/application/views/poiDetails.php. Here’s the pertinent code from the view:

<?php
require_once(APPPATH . "util/constants.php");
   // the sneaky bit.. tell xajax where to look for it's javascript files (web-accessible of course)
  $xajax->configure('javascript URI', base_url() . XAJAX_FOLDER );
  // this is the name of your controller. my controller was class View in view.php
  // so i have 'view' here.  what is your controller named?
  // this is another very sneaky bit.  we don't let it decide its own URI because
  // that only works if you are coming from the index() function in your
  // controller!!
  $xajax->setRequestURI(site_url('view'));
  // now print what we just configured
  $xajax->printJavascript();
?>
<!-- and finally a link to click on -->
<div id=lnkFav><a href='#' onclick="xajax_addFavorite();return false;">Add to Favorites</a></div>

Don’t forget the return false; after your xajax call and the # sign for the href value or your browser will take you to another page or jump to the top of the current page.

That’s it! There were a couple of sneaky things in there that took me forever to figure out, but hopefully I’ve saved you some measure of the pain I know.