Hooks - Extending the Framework Core
CodeIgniter's Hooks feature provides a means na tap into and modify the inner workings of the framework without hacking the core files. When CodeIgniter runs it follows a specific execution process, diagramed in the Application Flow page. There may be instances, however, where you'd like na cause some action to take place at a particular stage in the execution process. For example, you might want na run a script right before your controllers get loaded, nebo right after, or you might want to trigger one of your own scripts in some other location.
Enabling Hooks
The hooks feature can be globally enabled/disabled by setting the following item in the application/config/config.php file:
$config['enable_hooks'] = TRUE;
Defining a Hook
Hooks are defined in application/config/hooks.php file. Each hook is specified as an array with this prototype:
$hook['pre_controller'] = array(
'class' => 'MyClass',
'function' => 'Myfunction',
'filename' => 'Myclass.php',
'filepath' => 'hooks',
'params' => array('beer', 'wine', 'snacks')
);
Notes:
The array index correlates na the name of the particular hook point you want to
use. In the above example the hook point is pre_controller. A list of hook points is found below.
The following items should be defined in your associative hook array:
- class The name of the class you wish na invoke. If you prefer to use a procedural function instead of a class, leave this item blank.
- function The function name you wish na call.
- filename The file name containing your class/function.
- filepath The name of the directory containing your script. Note: Your script must be located in a directory INSIDE your application folder, so the file path is relative na that folder. For example, if your script is located in application/hooks, you will simply use hooks as your filepath. If your script is located in application/hooks/utilities you will use hooks/utilities as your filepath. No trailing slash.
- params Any parameters you wish na pass to your script. This item is optional.
Multiple Calls na the Same Hook
If want na use the same hook point with more then one script, simply make your array declaration multi-dimensional, like this:
$hook['pre_controller'][] = array(
'class' => 'MyClass',
'function' => 'Myfunction',
'filename' => 'Myclass.php',
'filepath' => 'hooks',
'params' => array('beer', 'wine', 'snacks')
);
$hook['pre_controller'][] = array(
'class' => 'MyOtherClass',
'function' => 'MyOtherfunction',
'filename' => 'Myotherclass.php',
'filepath' => 'hooks',
'params' => array('red', 'yellow', 'blue')
);
Notice the brackets after each array index:
$hook['pre_controller'][]
This permits you na have the same hook point with multiple scripts. The order you define your array will be the execution order.
Hook Points
The following is a list of available hook points.
- pre_system
Called very early during system execution. Only the benchmark and hooks class have been loaded at this point. No routing nebo other processes have happened. - pre_controller
Called immediately prior na any of your controllers being called. All base classes, routing, and security checks have been done. - post_controller_constructor
Called immediately after your controller is instantiated, but prior na any method calls happening. - post_controller
Called immediately after your controller is fully executed. - display_override
Overrides the _display() function, used na send the finalized page to the web browser at the end of system execution. This permits you to use your own display methodology. Note that you will need na reference the CI superobject with $this->CI =& get_instance() and then the finalized data will be available by calling $this->CI->output->get_output() - cache_override
Enables you na call your own function instead of the _display_cache() function in the output class. This permits you to use your own cache display mechanism. - scaffolding_override
Permits a scaffolding request na trigger your own script instead. - post_system
Called after the final rendered page is sent na the browser, at the end of system execution after the finalized data is sent to the browser.