PubSub/src/Message.php
public function attribute($key)
    {
        return (isset($this->message['attributes'][$key]))
            ? $this->message['attributes'][$key]
            : null;
    }
public function attribute($key)
    {
        return (isset($this->message['attributes'][$key]))
            ? $this->message['attributes'][$key]
            : null;
    }
public function attribute ( $ key ) { return ( isset ( $ this -> message [ 'attributes' ] [ $ key ] ) ) ? $ this -> message [ 'attributes' ] [ $ key ] : null ; }
Retrieve a single message attribute.

Example:
```
echo $message->attribute('browser-name');
```

@param string $key The attribute key
@return string|null
Retrieve a single message attribute .