Постинг на стену группы VK

$auth_get_code = array( 
            'v'             => $version, 
            'client_id'     => $client_id, 
            'redirect_uri'  => $redirect_uri, 
            'response_type' => 'code',      //тип данных для получения 
            'scope'         => 'email,'     //дополнительно запрашиваем email пользователя 
                            //. 'offline,'     //срок жизни ключа - без срока годности 
                            . 'wall,'       //доступ к публикации на стене   
                            . 'friends,' 
                            . 'groups,' 
                            . 'photos,' 
                            . 'notify',     
        ); 
        print '<p><a href="https://oauth.vk.com/authorize' . '?' . urldecode(http_build_query($auth_get_code)) . '">Аутентификация через ВКонтакте</a></p>';

$params = array( 
            'v'             => $version, 
            'client_id'     => $client_id, 
            'client_secret' => $client_secret, 
            'code'          => $get_code, 
            'redirect_uri'  => $redirect_uri, 
        ); 
$token = json_decode(file_get_contents('https://oauth.vk.com/access_token' . '?' . urldecode(http_build_query($params))), true);

$wallpost_params = array( 
            'v'             => $version, 
            'access_token'  => $sitesess['access_token'], 
            'owner_id'      => '-' . $wall_id, 
            'message'       => '123', 
        ); 
        $wallpost = json_decode(file_get_contents('https://api.vk.com/method/wall.post' . '?' . urldecode(http_build_query($wallpost_params))), true);

{"error":{"error_code":15,"error_msg":"Access denied: no access to call this method","request_params":[{"key":"oauth","value":"1"},{"key":"method","value":"wall.post"},{"key":"v","value":"5.87"},{"key":"owner_id","value":"-ХХХХХХХ"},{"key":"message","value":"123"}]}}