# getClientId

Learn how to provide the stored client ID.

An implementation must return the client ID stored for the current visitor, or `null` when none is set.

## Signature

This method has the following signature:

```php
public function getClientId(): ?Uuid
```

This method returns the stored client ID as a [`Uuid`](/reference/sdk/php/api/storage/uuid), or `null` when none is set.