# Overview

Discover the operations provided by the SDK.

This interface defines the operations you call on an SDK instance, such as fetching personalized content, evaluating queries, and managing the visitor identity.

The SDK's [entry point](/reference/sdk/php/api/core/croct) implements it, and you obtain an instance from one of its factories.

> **Type against the interface**
>
> Prefer the `Plug` interface to the concrete [`Croct`](/reference/sdk/php/api/core/croct) class in your type hints. Coding against the interface keeps your application decoupled from the SDK and lets you mock it in tests.

## Implementations

- [Entry point](/reference/sdk/php/api/core/croct): Create and configure an SDK instance.