# Stats events with additional dimensions

Adding additional dimensions to a [StatsEvent](https://cherrycake.tin.cat/version-0.x/reference/core-classes/statsevent) class allows you to keep track of the event in relation to a certain identifier. The best way to understand this is via an example:

Imagine you want to trigger a StatsEvent every time a user in your web app logs in. A simple way of doing this would be to create a `StatsEventUserLogin` class just like we saw in the [Stats guide](https://cherrycake.tin.cat/version-0.x/guide/stats-guide) main section:

```php
<?php

namespace CherrycakeApp;

class StatsEventUserLogin extends \Cherrycake\Stats\StatsEvent {
	protected $timeResolution = \Cherrycake\Stats\STATS_EVENT_TIME_RESOLUTION_DAY;
	protected $typeDescription = "User login";
}
```

To trigger this StatsEvent in the example we saw in the [Creating a complete login workflow](https://cherrycake.tin.cat/version-0.x/guide/login-guide/creating-a-complete-login-workflow) section, we would do it in the `doLogin` method, like this:

```php
function doLogin($request) {
    global $e;
    $result = $e->Login->doLogin($request->email, $request->password);
    if (
        $result == \Cherrycake\Login\LOGIN_RESULT_FAILED_UNKNOWN_USER
        ||
        $result == \Cherrycake\Login\LOGIN_RESULT_FAILED_WRONG_PASSWORD
    ) {    
        $e->Output->setResponse(new \Cherrycake\Actions\ResponseTextHtml([
            "code" => \Cherrycake\Output\RESPONSE_OK,
            "payload" => $e->HtmlDocument->header()."Login error".$e->HtmlDocument->footer()
        ]));
    }
    else {
        $e->Stats->trigger(new StatsEventUserLogin);
        
        $e->Output->setResponse(new \Cherrycake\Actions\Response([
            "code" => \Cherrycake\Outut\RESPONSE_REDIRECT_FOUND,
            "url" => $e->Actions->getAction("loginGuideHome")->request->buildUrl()
        ]));
    }
}
```

But what if we wanted to keep track of the times each individual user logs in? That's exactly what an additional dimension would do. In this case, the additional dimension would be the user's id.

To add the user id as an additional dimension to the `StatsEventUserLogin` class, we would modify it like this:

```php
<?php

namespace CherrycakeApp;

class StatsEventUserLogin extends \Cherrycake\Stats\StatsEvent {
    protected $timeResolution = \Cherrycake\Stats\STATS_EVENT_TIME_RESOLUTION_DAY;
    protected $typeDescription = "User login";
    protected $isSecondaryId = true;
    protected $secondaryIdDescription = "User id";

    function loadInline($data = false) {
        if ($data["userId"] ?? false)
            $this->secondary_id = $data["userId"];		
        return parent::loadInline($data);
    }
}
```

Notice we've added the `$isSecondaryId` and `$secondaryIdDescription` properties, and we overloaded the `StatsEvent::loadInline` method to retrieve the passed `userId` key and assign it to the `secondary_id` property. Don't forget to call the parent constructor at the end there.

So now, when triggering the `StatsEventUserLogin` event, we can pass the user's id like this:

```php
$e->Stats->trigger(new StatsEventUserLogin(["userId" => $e->Login->user->id]));
```

> You can create another additional dimension by setting the `$isTertiaryId` and `$tertiaryIdDescription` properties, and updating the `loadInline` method accordingly.

Using additional dimensions like this will add multiple rows to the database per each time frame and different dimension value, take into account that this will of course cause the stats table to grow a lot bigger.

{% hint style="success" %}
See this example working in the [Cherrycake documentation examples](https://documentation-examples.cherrycake.io/example/statsGuideAdditionalDimensions) site.
{% endhint %}