在应用程序上接收来自 FCM 的推送通知终止

Question

即使我（认为）满足文档中指定的所有条件，FCM onbackgroundmessage 也无法在应用程序上运行已终止。 这是正在发送的示例消息

<?php
    function sendNotification(){
        $server_token="AAAAksZAlDc:APA91bGLAfguJLdXmz65F-server token";
        $headers=array("Content-Type: application/json", "Authorization: key=$server_token");
    
        $url="https://fcm.googleapis.com/fcm/send";
        $ch= curl_init($url);
        
        curl_setopt($ch, CURLOPT_POST, true);
        $kita=time();
        $uid="dELAY-CRRm6z4ICpQP user  token";
        //$post_data= array("to"=> "$uid", "notification"=> array("title"=> "server title", "body"=>"Body from the server"));
        $kita= date("jS F Y h:i:a", time());
        $post_data= array("to"=> "/topics/sample_topic", "notification"=> array("title"=> "server title at $kita" , "body"=>"Body from the server"));
        
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($post_data));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        $resp= curl_exec($ch);
        curl_close($ch);
        echo "<p>Response is $resp</p>";
    }
    sendNotification();
?>

然后在我的 Flutter 应用中等待通知

FirebaseMessaging.onBackgroundMessage(fcmBGMsgs);
Future<void> fcmBGMsgs(remoteMessage){
  //defined outside every class
}

如果您有示例工作演示，请分享