# Google Auth Library Client - Class SignBlobInterface (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 SignBlobInterface.

Describes a class which supports signing arbitrary strings.

Classes which implement this interface in this package:

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

### signBlob

Sign a string using the method which is best for a given credentials type.

| **Parameters** ||
|---|---|
| **Name** | **Description** |
| `stringToSign` | `string` The string to sign. |
| `forceOpenssl` | `bool` Require use of OpenSSL for local signing. Does not apply to signing done using external services. **Defaults to** `false`. |

| **Returns** ||
|---|---|
| **Type** | **Description** |
| `string` | The resulting signature. Value should be base64-encoded. |

### getClientName

Returns the current Client Name.

| **Parameter** ||
|---|---|
| **Name** | **Description** |
| `httpHandler` | `callable|null` callback which delivers psr7 request, if one is required to obtain a client name. |

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