public function authenticate($auth = null)
    {
        if ($auth !== null) {
            $this->auth = $auth;
        }

        return $this->auth;
    }
public function authenticate($auth = null)
    {
        if ($auth !== null) {
            $this->auth = $auth;
        }

        return $this->auth;
    }
public function authenticate ( $ auth = null ) { if ( $ auth !== null ) { $ this -> auth = $ auth ; } return $ this -> auth ; }
Sets auth key

@param null|string $auth

@return string
Sets auth key