facebook - How to remove canvas_url from facebook app programmatically

Question

I'm trying to remove "App on Facebook" block in my application by doing this.

$fb = new Facebook(array(
    'appId' => <APPID>,
    'secret' => <APPSECRET>,
    'cookie' => true
));

$fbValues = array();
$fbValues['namespace'] = '';
$fbValues['canvas_url'] = '';
$fbValues['secure_canvas_url'] = '';
$facebookReturn = $fb->api('/151456581658184', 'post', $fbValues);

facebook returns ok, but the values does not change.

How can I unset this values other way?