PHP Hooks

PHP or code hook is a specially defined part in the program code that can pass control to an add-on. A hook is declared by calling a special function in the necessary part of code:

fn_set_hook('hook_name', $params, [$param2], [$paramN]);

Hooking is a very flexible technique; one function can have any number of hooks.

Review all available PHP hooks in all CS-Cart versions using the Hook base tool on our official website.

What a PHP Hook Looks Like in the Source Code

Here is an example of a PHP hook used in CS-Cart. It is declared in the function fn_get_gift_certificate_info used by the Gift certificates add-on:

fn_set_hook('get_gift_certificate_info', $_certificate, $certificate, $type)

When PHP Hooks Are Used

Hooks provide a convenient way for add-ons to perform additional actions in the middle of the main flow.

Knowing the hook name, any addon can intercept execution of the program code, perform necessary manipulations, and then return the execution process to the main program. When calling a certain hook, all variables directly defined in this hook become available for the addon.

A hook call within an add-on is carried out by defining the function which name consists of the prefix fn_, addon name, underscore and the full name of the called hook:

fn_gift_certificates_get_gift_certificate_info($_certificate, $certificate, $type)

So, according to the function name, the code inside the function will be executed in the hook get_gift_certificate_info in the Gift certificates add-on.

How to Use a PHP Hook

In order to use PHP hooks in your add-on:

  • Declare the hook to be used in the add-on init.php file:

      ...

fn_register_hooks(
   'get_category_data_pre'
);

  ...

  • Create a function to perform actions on the hook occurence in the add-on func.php file:

    <?php

if ( !defined('AREA') ) { die('Access denied'); }

function fn_my_addon_get_category_data_pre(&$category_id, &$field_list, &$get_main_pair, &$skip_company_condition, &$lang_code)
{
   ...
}

?>

And that’s it! The add-on is now “aware” that it should use the hook, and CS-Cart is aware that it should pass the control to the add-on when the hook occurs.

Extending one add-on with another

If it is necessary to extend one add-on with another, now it is possible to select all hook functionality inside the add-on. For example, the News and emails add-on uses SEO. Not to spread the SEO functionality across all the News and emails functionality, it can be passed to a hook:

design/backend/templates/addons/news_and_emails/addons/seo/hooks/

The principles of working are the same as for the other hooks. One exception is that hooks from the addons catalog inside the news_and_emails add-on will be included only when the appropriate add-on is enabled (the SEO add-on in this example).

The 3rd parameter was added for registering the php hooks:

fn_register_hooks( array('get_news_data', '', 'seo') )

The name of a function processing a hook is fn_seo_get_news_data. It is called out when the SEO add-on is enabled.

Note

All the actions described in the Extending one add-on with another section take place in the News and emails add-on.