# Google Auth Library Client - Class ExternalAccountCredentialSourceInterface (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 ExternalAccountCredentialSourceInterface.

Classes which implement this interface in this package:

- [CredentialSource\\AwsNativeSource](https://docs.cloud.google.com/php/docs/reference/auth/latest/CredentialSource.AwsNativeSource)
- [CredentialSource\\ExecutableSource](https://docs.cloud.google.com/php/docs/reference/auth/latest/CredentialSource.ExecutableSource)
- [CredentialSource\\FileSource](https://docs.cloud.google.com/php/docs/reference/auth/latest/CredentialSource.FileSource)
- [CredentialSource\\UrlSource](https://docs.cloud.google.com/php/docs/reference/auth/latest/CredentialSource.UrlSource)

## Namespace

Google \\ Auth

## Methods

### fetchSubjectToken

| **Parameter** ||
|---|---|
| **Name** | **Description** |
| `httpHandler` | `?callable` |

### getCacheKey