Gajus\Fuss\PageTab::__construct PHP Method

    public function __construct(\Gajus\Fuss\SignedRequest $signed_request)
    {
        $payload = $signed_request->getPayload();
        if (!isset($payload['page'])) {
            throw new Exception\PageTabException('Signed request does not describe page tab.');
        }
        $this->page = $payload['page'];
    }