Codeigniter Hooks Example

In this tutorial, we would love to share how to create, enable and use custom hooks in CodeIgniter projects.

CodeIgniter hooks allow you to execute a script with specific path within the CodeIgniter execution process without updating or modifying core files. If you need to execute a code that should be run every time a controller is created, you specify that script path in the hook.

Let’s start to create, enable and use hooks in CI:

Enabling Hooks

The hooks feature can be enabled or disabled by setting the following items in the app/config/config.php file.

$config['enable_hooks'] = TRUE;

Defining a Hook

The hooks are defined in the app / config / hooks folder. Each hook is specified as an array with this prototype:

$hook['pre_controller'] = array(
         'class' => 'MyHook', 
	 'function' => 'Myfunction', 
	 'filename' => 'MyHook.php', 
	 'filepath' => 'hooks', 
	 'params' => array('element1', 'element2', 'element3')
   );

1. $hook['pre_controller']: Specifies the hook point, which is “pre_controller”.
2. = array(: Indicates the start of the array defining hook settings.
3. 'class' => 'MyClassName',: Specifies the class name containing the method to be called.
4. 'function' => 'MyfunctionName',: Specifies the name of the function/method to be called.
5. 'filename' => 'Filename.php',: Specifies the file where the class containing the method is defined.
6. 'filepath' => 'hooks',: Specifies the directory path where the file containing the class is located.
7. 'params' => array('beers', 'wines'): Optional parameter that passes an array of parameters to the method/function being called.

Multiple calls to the same Hook

You can use multi-dimensional array to use the same hook point with more than one script, like this:

$hook['pre_controller'][] = array(
    'class' => 'MyClass', 
    'function' => 'Myfunction', 
    'filename' => 'Myclass.php', 
    'filepath' => 'hooks', 
    'params' => array('element1', 'element2', 'element3')
   );
$hook['pre_controller'][] = array(
    'class' => 'MyClass2', 
    'function' => 'Myfunction2', 
    'filename' => 'Myclass2.php', 
    'filepath' => 'hooks', 
    'params' => array('element4', 'element5', 'element6')
   );

Hook points

1. pre_system: Executes very early during system execution, loading only the hook class and benchmark.
2. pre_controller: Runs before controller invocation, after base classes, security checks, and routing.
3. post_controller_constructor: Runs immediately after controller instantiation, but before any method call.
4. post_controller: Executed right after the controller’s method has finished executing.
5. display_override: Allows overriding the default page display behavior at the end of file execution.
6. cache_override: Enables replacing the default caching method with a custom one.
7. post_system: Executed at the end of system execution, after sending finalized data to the browser.

How to Use Hooks?

Using a text editor, create a controller called Test.php In it, place this code and save it to your application/controllers/ directory:

<?php
   class Test extends CI_Controller { 
    
      public function index() { 
         echo " world !";
      }
  }
?>

Using a text editor, create a controller called myhook.php. In it, place this code and save it to your application/hooks/ directory:

<?php
   class Myhook extends CI_Controller { 
    
      public function index() { 
         echo "Hello";
      }
  }
?>

We need to define the hooks in the application/config/hooks.php file:

$hook['pre_controller'] = array(
    'class' => 'Myhook', 
    'function' => 'index', 
    'filename' => 'Myhook.php', 
    'filepath' => 'hooks', 
    'params' => array()
   );

Now open your site using a URL similar to this one:

http://localhost/codeigniter/index.php/test/index