# Core

Discover the SDK entry point and operations.

The core SDK API: [`Croct`](/reference/sdk/php/api/core/croct), the class you instantiate, and the [`Plug`](/reference/sdk/php/api/core/plug) interface it implements, which defines the operations you call.

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Use the summary below to quickly jump to a specific topic:

- [Croct](/reference/sdk/php/api/core/croct): Learn how to create the SDK.
- [Plug](/reference/sdk/php/api/core/plug): Discover the operations provided by the SDK.