How can I receive all the messages send to a topic of MQTT to a webpage everytime I load the index?

So I’m new to MQTT and I have to make a “messaging” project that loads all the messages (sent to a certain topic) in my index page without a long load time, I’m working with Yii2 Framework Advanced Project and I’ve already done the publish code, in the model I created the AfterSave method and everytime it saves something to the database it publishes one message to my MQTT Broker that is in my Raspberry PI

Example

I own a hotel and everytime I login to my backend I want to have in my index all the reservation requests that were sent to this topic in MQTT mosquitto “request-reservation” (like a notification).

Like I said I’m working with Yii2 Framework Advanced Project and the extension that I’m using for MQTT is BluerhinosphpMQTT

Code that I already have:

Class Model ReservationRequest.php (this is working and sending to the topic because I already tested in the shell)

public function afterSave($insert, $changedAttributes) {
        parent::afterSave($insert, $changedAttributes); // TODO: Change the autogenerated stub
        if ($insert){
            $this->publish("request-reservation", "New notification of a reservation request with the ID: '. $this->id . PHP_EOL");
        }
}

Any advice is welcome, and thanks for the attention

Answer

Sort answer is you don’t.

MQTT is not a message queuing system. It will only queue messages that have not been delivered to a client with a persistent subscription that is is currently that is offline at the time the message is sent.

You probably have 2 options

1. Publish a single message with the current state of all the rooms, e.g. { "room1": "occupied", "room2": "free",...} and set the retained flag so the latest version of this message will always be delivered to a client when they subscribe to that topic.

2. Make a REST call to the backend that can run a query on the database to retrieve the current state of all the rooms.