Controllers

Controllers are the heart of your application, as they determine how HTTP requests should be handled.

• What is a Controller?
• Hello World
• Functions
• Passing URI Segments to Your Functions
• Defining a Default Controller
• Remapping Function Calls
• Controlling Output Data
• Private Functions
• Organizing Controllers into Sub-folders
• Class Constructors
• Reserved Function Names

What is a Controller?

A Controller is simply a class file that is named in a way that can be associated with a URI.
Consider this URI:
example.com/index.php/blog/

 In the above example, CodeIgniter would attempt to find a controller named blog.php and load it.

When a controller's name matches the first segment of a URI, it will be loaded.

Let's try it:  Hello World!

Let's create a simple controller so you can see it in action. Using your text editor, create a file called blog.php, and put the following code in it:

<?php class Blog extends CI_Controller { public function index() { echo 'Hello World!'; } } ?>
Then save the file to your application/controllers/ folder.
Now visit the your site using a URL similar to this:

example.com/index.php/blog/

 If you did it right, you should see Hello World!.

Note: Class names must start with an uppercase letter. In other words, this is valid:

<?php
class Blog extends CI_Controller {

}
?> This is not valid:
<?php
class blog extends CI_Controller {

}
?>

 Also, always make sure your controller extends the parent controller class so that it can inherit all its functions.