# Google Auth Library Client - Class ProjectIdProviderInterface (1.50.1)

1.50.1 (latest) 1.50.0 1.49.0 1.48.1 1.47.1 1.46.0 1.45.2 Reference documentation and code samples for the Google Auth Library Client class ProjectIdProviderInterface.

Describes a Credentials object which supports fetching the project ID.

Classes which implement this interface in this package:

- [Credentials\\ExternalAccountCredentials](https://docs.cloud.google.com/php/docs/reference/auth/latest/Credentials.ExternalAccountCredentials)
- [Credentials\\GCECredentials](https://docs.cloud.google.com/php/docs/reference/auth/latest/Credentials.GCECredentials)
- [Credentials\\ServiceAccountCredentials](https://docs.cloud.google.com/php/docs/reference/auth/latest/Credentials.ServiceAccountCredentials)
- [Credentials\\ServiceAccountJwtAccessCredentials](https://docs.cloud.google.com/php/docs/reference/auth/latest/Credentials.ServiceAccountJwtAccessCredentials)
- [FetchAuthTokenCache](https://docs.cloud.google.com/php/docs/reference/auth/latest/FetchAuthTokenCache)

## Namespace

Google \\ Auth

## Methods

### getProjectId

Get the project ID.

| **Parameter** ||
|---|---|
| **Name** | **Description** |
| `httpHandler` | `callable|null` Callback which delivers psr7 request |

| **Returns** ||
|---|---|
| **Type** | **Description** |
| `string|null` |   |