How to create a real-time weather forecast application using PHP and MQTT

How to use PHP and MQTT to create a real-time weather forecast application

Introduction:
Weather forecast is a very important service in our lives. With the development of the Internet of Things and instant communication technology, we can Use MQTT (Message Queuing Telemetry Transport) protocol to obtain real-time weather data. In this article, I will introduce how to use PHP and MQTT to create a real-time weather forecast application. Through this application, we can subscribe to specific weather station channels and get data such as temperature, humidity, and wind direction in real time.

Subject:

Step 1: Install MQTT server
First, we need to install an MQTT server so that we can connect to the weather station and get real-time data. There are many MQTT servers to choose from, such as Mosquitto, EMQ X or HiveMQ, etc. In this article, we will use Mosquitto as it is a popular and free open source MQTT server. You can download and install it from Mosquitto’s official website.

Step 2: Create a weather forecast application
Next, we need to create a PHP script to subscribe to weather data and display it in the application. We will use a popular PHP MQTT client library such as phpMQTT.

First, download the phpMQTT library from GitHub and import it into the project using the following command:

git clone https://github.com/bluerhinos/phpMQTT.git

Next, create an index.php file and import the phpMQTT library:

<?php
require("phpMQTT.php");

Then, create an MQTT client instance and connect to the MQTT server:

<?php
require("phpMQTT.php");

$server = "localhost";  // MQTT服务器的主机名或IP地址
$port = 1883;  // MQTT服务器的端口号
$client_id = "weather_app";  // 定义客户端ID

$mqtt = new phpMQTT($server, $port, $client_id);
if ($mqtt->connect()) {
    echo "Connected to MQTT server.
";
    // 订阅气象站频道
    $mqtt->subscribe("weather_station/#", 0);
    
    // 持续循环以接收来自气象站的消息
    while ($mqtt->proc()) {
    }
} else {
    echo "Failed to connect to MQTT server.
";
}
$mqtt->close();
?>

In the above code, we connect to the MQTT server and subscribe to the "weather_station/#" channel, indicating that we will receive All messages starting with "weather_station/". You can replace this channel with the channel of your actual weather station.

Then, we need to process the received message in a callback function. In this function we can parse and display weather data.

<?php
require("phpMQTT.php");

// ...

function messageReceived($topic, $payload) {
    // 接收到消息时调用此函数
    $data = json_decode($payload, true);
    
    // 解析天气数据
    $temperature = $data['temperature'];
    $humidity = $data['humidity'];
    $wind_direction = $data['wind_direction'];
    
    // 显示天气数据
    echo "Temperature: ".$temperature."°C
";
    echo "Humidity: ".$humidity."%
";
    echo "Wind Direction: ".$wind_direction."
";
}

$mqtt->debug = true;
$mqtt->onMessage('messageReceived');

In the above code, we parse the received JSON string into an associative array and extract the temperature, humidity and wind direction data from it. Then we display the data on the screen.

Step 3: Set up the weather station
Finally, we need to set up a weather station and publish real-time weather data. You can use any hardware device compatible with the MQTT protocol to send data. A common option is to use an ESP8266 chip and a DHT11 sensor. We won't go into the specific hardware setup here, but it's up to you to choose and configure it to suit your needs.

The code example for publishing weather data on the MQTT server is as follows:

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// 定义WiFi连接信息
const char* ssid = "your_wifi_ssid";
const char* password = "your_wifi_password";

// 定义MQTT服务器信息
const char* mqtt_server = "mqtt_server_ip";
const char* mqtt_topic = "weather_station";

WiFiClient espClient;
PubSubClient mqttClient(espClient);

void setup() {
  // 连接WiFi
  WiFi.begin(ssid, password);
  
  // 连接MQTT服务器
  mqttClient.setServer(mqtt_server, 1883);
  
  // 设置回调函数
  mqttClient.setCallback(callback);
  
  // 读取传感器数据并发布
  float temperature = readTemperature();
  float humidity = readHumidity();
  String windDirection = readWindDirection();
  publishData(temperature, humidity, windDirection);
}

void loop() {
  // 接收MQTT消息
  mqttClient.loop();
}

void callback(char* topic, byte* payload, unsigned int length) {
  // 不处理接收消息的回调函数
  // 可以添加自己的逻辑以处理接收到的消息
}

void publishData(float temperature, float humidity, String windDirection) {
  // 构造JSON字符串
  String json = "{"temperature":" + String(temperature) + ",";
  json += ""humidity":" + String(humidity) + ",";
  json += ""wind_direction":"" + windDirection + ""}";
  
  // 发布消息到MQTT服务器
  mqttClient.publish(mqtt_topic, json.c_str());
}

In the above code, we first connect to the WiFi network and then connect to the MQTT server. We then read the sensor data (such as temperature, humidity, and wind direction) and encapsulate it as a JSON string. Finally, we publish the message to the "weather_station" channel on the MQTT server.

Conclusion:
By using PHP and MQTT, we can easily create a real-time weather forecast application. We can subscribe to weather data and display real-time temperature, humidity and wind direction information in the app. This app helps us better understand current weather conditions and make decisions accordingly.

Please note that the code example provided in this article is a basic framework and can be extended and modified to meet your specific needs. To use this application, you need to adapt your hardware device and MQTT server settings.

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