> For the complete documentation index, see [llms.txt](https://circular-protocol.gitbook.io/standard-apis/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://circular-protocol.gitbook.io/standard-apis/api-docs/php/signmessage.md).

# signMessage()

**Method Signature:**

```php
private function signMessage($message, $privateKey)
```

**Parameters**

| Name         | Type   | Description                                                         |
| ------------ | ------ | ------------------------------------------------------------------- |
| `message`    | string | Message that you want to sign. In transactions it must be the TxID. |
| `privateKey` | string | Private key in hexadecimal format.                                  |

**Example**

```php
<?php
require 'vendor/autoload.php';
use CircularProtocol\Api\CircularProtocolAPI;

$circular = new CircularProtocolAPI();
$message = "Hello, World!";
$address = "0x8b1dd25076c04c5139acba458f86c69cd2d322c61d19bc28daa3bbd945083738";

$result = $circular->signMessage($message, $address);
```

**Result**

The result will be of type `String`

```json
af14525076c04c5139acba458f86c69cd2d322c61d19bc28daa3bbd9450837ab
```