# Event Tracking

The Hackle SDK provides the ability to send user events to Hackle. By using this feature at every point where a change in user behavior occurs, you can obtain meaningful data about user behavior, and analyze user behavior through the collected data.

## track

You can send user events by passing an **Event Key** and **User Identifier** to the `track()` method.

### Event Name (key)

* It is recommended to name it like a typical variable name but make it easy to identify.
* Character limit is 128 characters. (128 characters)

### Example

Assume you have defined an Event Key called `purchase` to collect events when a user clicks the purchase button.

```php
<?php

require 'vendor/autoload.php';

$client = \Hackle\HackleClients::create("YOUR_SDK_KEY");

// "ae2182e0"라는 식별자를 가진 사용자가 발생시킨 "purchase"라는 이벤트를
// 숫자 값과 함께 전송
$user = \Hackle\Common\HackleUser::builder()
    ->deviceId("ae2182e0")
    ->build();
$event = \Hackle\Common\HackleEvent::builder("purchase")
    ->property("pay_method", "CARD")
    ->property("discount_amount", 800)
    ->property("is_discount", true)
    ->build();

$client->track($event, $user);

?>
```

## Property

The Hackle SDK supports adding properties to Event objects.

* A property must be sent as a pair of a Property Key (key) and a Property Value (value).
* The maximum number of properties that can be added to an event object is 64.

<table><thead><tr><th width="133.04296875">Category</th><th width="127.60546875">Type</th><th>Constraints</th></tr></thead><tbody><tr><td>Property Key</td><td><code>string</code></td><td><ul><li>Character limit is 128 characters.</li><li>Case-insensitive.</li><li>For example, AGE and age are recognized as the same Property Key.</li></ul></td></tr><tr><td>Property Value</td><td><code>boolean</code>, <code>string</code>, <code>number</code>, <code>array</code></td><td><ul><li>For string type, the character limit is 1024 characters.</li><li>String type is case-sensitive.</li><li>For example, APPLE and apple are recognized as different Property Values.</li><li>For number type, up to 15 integer digits and up to 6 decimal places are supported.</li></ul></td></tr></tbody></table>


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