PHP Hooks¶

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 add-on 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 add-on.

A hook call within an add-on is carried out by defining the function which name consists of the prefix fn_, add-on 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.