GCM设置推送通知的截止日期

我使用PHP成功地为我的android用户发送GCM推送通知，但我想设置推送通知的截止日期，以便在用户没有互联网连接1周的情况下，它将不会收到旧的推送通知。我是如何做到的。

谢谢。这是php代码:

 private $GOOGLE_API_KEY = "XXXXX";
    public function send($registration_id, $data) {
        // include config
        // Set POST variables
        $url = 'https://android.googleapis.com/gcm/send';
        $fields = array(
            'registration_ids' => $registration_id,
            'data' => $data,
        );
        $headers = array(
            'Authorization: key=' . $this->GOOGLE_API_KEY,
            'Content-Type: application/json'
        );
        // Open connection
        $ch = curl_init();
        // Set the url, number of POST vars, POST data
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        // Disabling SSL Certificate support temporarly
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));
        // Execute post
        $result = curl_exec($ch);
        if ($result === FALSE) {
            die('Curl failed: ' . curl_error($ch));
        }
        // Close connection
        curl_close($ch);
        // echo $result;
    }