Real-time water quality monitoring using PHP and MQTT

As people pay more and more attention to health and environmental protection, their requirements for water quality are also getting higher and higher. Through real-time water quality monitoring, we can understand water quality conditions in a timely manner and ensure the safety of people's drinking and domestic water sources. This article will introduce how to use PHP and MQTT technology to achieve real-time water quality monitoring.

1. Introduction to MQTT

MQTT (Message Queuing Telemetry Transport) is a lightweight communication protocol mainly used for instant communication between IoT devices. The MQTT protocol adopts the publish/subscribe (Publish/Subscribe) mode to implement message distribution and routing through Broker. Simply put, the Publisher publishes messages to all subscribers, and the Subscriber receives messages by subscribing to a topic of interest.

The MQTT protocol has the following characteristics:

1. Lightweight: The protocol is simple, has low overhead, and is suitable for communication between small devices.
2. High reliability: Ensure the correctness and reliability of message transmission.
3. Flexible routing: Able to route messages according to actual conditions.
4. Security: Supports SSL/TLS encrypted transmission, which can protect the security of message transmission.

2. PHP implements MQTT communication

The implementation of the MQTT protocol requires the use of specific client libraries, such as Paho MQTT, Mosquitto, etc. In PHP, we can use the phpMQTT class library to implement MQTT communication. It is a simple and easy-to-use PHP MQTT client library.

The steps to use phpMQTT are as follows:

1. Install the phpMQTT class library:

composer require bluerhinos/phpmqtt

2. Use the class library:

require("phpMQTT.php");

$mqtt = new phpMQTT("test.mosquitto.org", 1883, "ClientID".rand());
if ($mqtt->connect()) {
    $mqtt->publish("Topic", "Hello World! QoS 0", 0);
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT broker";
}

In the above code, we created a phpMQTT object through the new keyword, passed in the Broker's address and port number, and a randomly generated ClientID. Next, we connect to the MQTT Broker using the connect() method and publish the message using the publish() method.

3. Real-time water quality monitoring

In real-time water quality monitoring, we need to collect water quality data and send the data to MQTT Broker. In order to simulate data collection, we can use a random number generation function to generate water quality indicators such as water temperature, pH value, and dissolved oxygen.

The following is a PHP function that generates random water quality data:

function generateWaterData() {
    $temp = rand(20, 30);
    $ph = (float)rand(60, 80) / 10;
    $do = rand(5, 11);
    return array(
        "temperature" => $temp,
        "pH" => $ph,
        "dissolved_oxygen" => $do
    );
}

After generating the water quality data, we need to send the data to the MQTT Broker. We can use the publish() method provided by the phpMQTT class library to achieve this:

$mqtt = new phpMQTT("test.mosquitto.org", 1883, "ClientID".rand());

if ($mqtt->connect()) {
    while (true) {
        $waterData = generateWaterData();
        $mqtt->publish("water_quality", json_encode($waterData), 0);
        sleep(5);
    }
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT broker";
}

In the above code, we first create an mqtt object and connect to the MQTT Broker. Next, we use a while loop to continuously generate random water quality data and publish it to the water_quality topic through the publish() method.

Finally, we can subscribe to the topic through MQTT to receive and process water quality data. In PHP, we can use the subscribe() method provided by the phpMQTT class library:

$mqtt = new phpMQTT("test.mosquitto.org", 1883, "ClientID".rand());

if ($mqtt->connect()) {
    $topics["water_quality"] = array("qos" => 0, "function" => "processWaterData");
    $mqtt->subscribe($topics, 0);
    while ($mqtt->proc()) {
        // 运行代码
    }
    $mqtt->close();
} else {
    echo "Failed to connect to MQTT broker";
}

function processWaterData($topic, $msg) {
    $waterData = json_decode($msg);
    // 处理水质数据
}

In the above code, we first create an mqtt object and connect to the MQTT Broker. Next, we subscribed to the water_quality topic using the subscribe() method and specified the message processing function processWaterData. Finally, we use the proc() method to maintain the connection and wait to receive MQTT messages at any time. By processing the received water quality data in the processWaterData() function, we can achieve the goal of real-time water quality monitoring.

Summary

This article introduces how to use PHP and MQTT technology to achieve real-time water quality monitoring. Through the phpMQTT class library, we can easily connect to the MQTT Broker and implement data publishing and subscription functions. Applying the MQTT protocol to real-time water quality monitoring can not only improve the real-time and reliability of data transmission, but also help us grasp water quality conditions in a timely manner and ensure the safety of people's drinking water.

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