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A Quick Code Igniter and JQuery Ajax Tutorial

This tutorial assumes a basic working knowledge of Code Igniter. If you have never used CI before, please refer to the framework documentation

In the old days (2 years ago), working the Javascript magic to create a cool AJAX based event took a fairly decent working knowledge of the mechanisms behind the process.

With the increasing popularity of Javascript libraries however, this type of functionality became available to the web site hobbyist, and was made much easier for the web site professional.

The following step-by-step tutorial will show you how to combine the power of JQuery (a javascript library that weighs in at about 20k) with Code Igniter (a PHP framework based on the MVC design pattern) to quickly and painlessly pass a record ID through the javascript and over to the server, where it will be passed to a mysql database, used to retrieve some data, and sent back to the page for display.

Step 1
We begin by assuming that you have a div with an id of content, which is where you would like your freshly retrieved data to display, once it has been freshly retrieved. For this exercise, you have already taken an action to call your javascript function with a record ID parameter.

The first thing you need to do, is make sure JQuery is being loaded, and to create a function for your AJAX request.

Step 2:
Next, youll use the JQuery function load, and attach it to your content div:

function get_record_id(record_id) {
     $('#content').load()
}

Step 3:
The load function accepts three arguments. The page to be called on the other side of the HTTPRequest, the array to pass through the POST, and a callback function. It looks like this:

function get_record_id(record_id) {
     $('#content').load(/controller/method,p,function(str){

	 });
}

Lets go back to that. Code Igniter URLs are created by calling the name of your controller, followed by the function inside the controller class that will handle your request. If your server does not support mod-rewrite, you may also need to append an index.php to the beginning. The str inside the callback function is the results of your AJAX request. There isnt much use for the str when using the .load function, but it does come in handy using the other JQuery AJAX functions – $.post and $.get, which I assume are self explanatory.

Step 4

var p = {}; //instantiate the array
p[record_id] = record_id //assign your record_id variable to it.

Thats all there is to it. Your final javascript function looks like this:

function get_record_id(record_id) {
     var p = {};
     p[record_id] = record_id
     $('#content').load(/controller/method,p,function(str){

     });
}

Step 5
On the CI side, you have a controller and method setup something like this:

class Controller
{
   function Controller()
   {
       parent::CI;
   }

   function method()
   {
   }
}

The important part is the method() function, as it will contain some of the code we need to make things happen.

Step 6
The first thing you need to do on the CI side is retrieve the value passed through the request object. This is simple enough, using $_POST[record_id]. You also want to load up your database model so you can get the record out of your database. So, well load the database library, and then load the actual model. Then, we want to send the record ID to the database, get the resulting data, and pass it back out to the request. our function starts to look like its doing something useful pretty quickly.

function method()
{
   $record_id = $_POST[record_id];
   //set the record ID
   $this->load->library(database);
   //load the database library to connect to your database
   $this->load->model(records);
   //inside your system/application/models folder, create a model based on the procedure
   //outlined in the CI documentation
   $results = $this->records->get_record($record_id);
   //get the record from the database
}

Step 7
At this point, we need to go into our records.php file in the model folder. Since Code Igniter uses a Model-View-Controller structure, database activity, server-side processing, and client-side display should be as separate from one another as possible. You dont NEED to do this for Code Igniter to do its thing, but its good practice.

Inside the records.php file, well create a method called get_record to match the method referenced above. Well use it to get a record by its primary key of ID, put the resulting data into an array, and send it back to the controller, out to the view, and ultimately into the content div we started with.

function get_record($record_id)
{
   $this->db->where(ID,$record_id);
   //we want the row whose ID matches the value were passing in
   $query = $this->db->get(record_table);
   //get the table and put it into an object named $query
   $row = $query->row();
   //gets the first row of the resulting dataset.  In this case, only 1 row will ever be returned
   $results[record][$row->ID][name] = $row->name;
   //here, we create a multi-dimensional array holding the returned values
   //based on the key.
   return $results;
   //send the record back to the controller
}

The trickiest part of this section is the array. It seems pretty complex from here, but youll see soon enough how it breaks down into something more manageable as we go along.

Step 8
Were back to the controller again, and we have one more line to add – this time to pass the resulting data into a view to be formatted and printed to the content div. The whole method() function now looks like this:

function method()
{
   $ID = $_POST[record_id];  //set the record ID
   $this->load->library(database);
   //load the database library to connect to your database
   $this->load->model(records);
   //inside your system/application/models folder, create a model based on
   //the procedure outlined in the CI documentation
   $results = $this->records->get_record($record_id);
   //get the record from the database
   $this->load->view(AJAX_record,$results);
}

Step 9
The AJAX_record.php file should be in your system/application/views folder. Keep in mind, that when you pass an array to a view (in this case the $results array), it will be exploded inside the view. So, the path to your record is now $record, instead of $results[record]. Also inside will be your standard HTML markup, and something like this:

< ?php foreach($record as $id=>$value) { ?>
     The name associated with this record is: < ?php print $value[name];?>
< ?php } ?>

This output is what php is sending to the request object, and is also what gets loaded into the content div. Code Igniter and JQuery make it that easy to dynamically load data using AJAX.

Referenced by: http://www.mrforbes.com/blog/2009/01/a-quick-code-igniter-and-jquery-ajax-tutorial/

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Posted by on March 2, 2011 in CodeIgniter, JQuery, jQuery for PHP, PHP