src/Google/Client.php
public function revokeToken($token = null)
  {
    $tokenRevoker = new Google_AccessToken_Revoke(
        $this->getHttpClient()
    );

    return $tokenRevoker->revokeToken($token ?: $this->getAccessToken());
  }
public function revokeToken($token = null)
  {
    $tokenRevoker = new Google_AccessToken_Revoke(
        $this->getHttpClient()
    );

    return $tokenRevoker->revokeToken($token ?: $this->getAccessToken());
  }
Revoke an OAuth2 access token or refresh token. This method will revoke the current access
token, if a token isn't provided.

@param string|array|null $token The token (access token or a refresh token) that should be revoked.
@return boolean Returns True if the revocation was successful, otherwise False.