> For the complete documentation index, see [llms.txt](https://docs.minical.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.minical.io/build-an-extension/build-your-first-extension/hooks.md).

# Hooks

Under the hooks folder, we have 2 files actions.php and filters.php

```
----->hooks
      |----->actions.php
      |----->filters.php
```

**Actions**

Action is one of the two types of hooks. They provide a way for running a function at a specific point in the execution of miniCal Core. Callback functions for an Action do not return anything to the calling Action hook. You can create a hook in the application/hooks folder, here we have created an actions.php file.\
You can find the list of actions here [miniCal Action list](https://github.com/minical/minical/wiki/The-list-of-the-miniCal-actions).

```php
//file name actions.php
// This is a core action that will be executed when a new reservation is created in miniCal
add_action('add.booking.created', 'your_callback_function_1', 10, 1);
function your_callback_function_1($data) {
    // code here
}


// This is a custom action and can be executed from this extension controllers.
add_action('my-custom-action', 'your_custom_callback_function', 10, 1);
function your_custom_callback_function($data) {
    // code here
}
```

**Filters**

They provide a way for functions to modify data during the execution of the miniCal Core. They are the counterpart to action. You can create a hook in the application/hooks folder, here we have created a filers.php file.

{% code title="filters.php" %}

```php
// This is a custom action and can be executed from this extension controllers.
add_filter('my-custom-filter', 'your_callback_function_2', 10, 1);
function your_callback_function_2($data) {
    
    // start writing code here
    // return $data;
}
```

{% endcode %}