public function clientId()
	{
		if (isset($this->client_id)) {
			return $this->client_id ? $this->client_id : null;
		}
		
		if (!$this->check()) {
			return null;
		}
		
		if (Request::input('client_id')) {
			$this->client_id = Request::input('client_id');
		}
		else if ($id = Authorizer::getClientId()) {
			$this->client_id = $id;
		}
		else {
			$this->client_id = false;
		}
		
		return $this->client_id ? $this->client_id : null;
	}