> 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/minical-filters.md).

# miniCal Filters

Filters are functions that always accept data in the form of an Argument and, after processing again, return the data as Return Value. The filter itself means the process of filtering something out. Just like the do\_action, here we have the apply\_filters() function.

```php
$filtered_value = apply_filters('example_filter_to_run', $arg );
```

So, now the $filtered\_value will be the system-generated output until you add a filter on it. In order, add the filter you need to call add\_filter() just like the add\_action(). Below is the example :

```php
// The filter callback function is based on the filter.

add_filter( ‘example_filter_to_run’, ‘example_callback_fun’, 10, 1 );

function example_callback_fun($arg) {
// code
return $arg;
}
```

**Customer Filters List**

| METHOD         | NAME                 | PARAMETERS | USE CASE                           |
| -------------- | -------------------- | ---------- | ---------------------------------- |
| apply\_filters | post.add.customer    | $data      | After the creation of new customer |
| apply\_filters | post.update.customer | $data      | After updating a customer          |

**Payment Source Filters List**

| METHOD         | NAME                        | PARAMETERS | USE CASE                                            |
| -------------- | --------------------------- | ---------- | --------------------------------------------------- |
| apply\_filters | post.create.payment\_source | $data      | After the creation of customer's new payment source |
| apply\_filters | post.update.payment\_source | $data      | After updating a customer's payment source          |
| apply\_filters | post.delete.payment\_source | $data      | After deleting a customer's payment source          |