How to use PHP to implement the pull-down refresh function in WeChat applet

With the popularity of WeChat mini programs, many developers have begun to use PHP language to build WeChat mini program background services. Pull-down refresh is a very common interactive function in mini programs. This article will introduce how to use PHP to implement the pull-down refresh function in WeChat mini programs.

1. The principle of pull-down refresh in the WeChat applet

In the WeChat applet, the principle of pull-down refresh is that the client initiates an HTTP request to the server, and then the server returns the latest data to the client. After the client gets the data, it uses JavaScript to render the latest data onto the page.

2. Use PHP to implement the pull-down refresh function in the WeChat applet

1. Create a PHP file

First create a file named "refresh.php ” PHP file, used to handle HTTP requests initiated by the client.

2. Connect to the database

Use the mysqli extension in the PHP file to connect to the database and verify whether the database is successfully connected. The code is as follows:

<?php
$servername = "localhost"; //数据库主机名
$username = "username"; //数据库用户名
$password = "password"; //数据库密码
$database = "database"; //数据库名称

// 创建连接
$conn = new mysqli($servername, $username, $password, $database);

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}
echo "连接成功";
?>

3. Query The latest data

The operation of querying data uses SQL statements. The mysqli_query() function executes the SQL statement to obtain the latest data from the database. The code is as follows:

$sql = "SELECT * FROM table_name ORDER BY publish_time DESC LIMIT 10";
$result = mysqli_query($conn, $sql);

The above code uses " table_name" is used as the name of the data table, and is arranged in reverse order by publish_time to query the first 10 pieces of data.

4. Return the data to the client

Finally, the queried data is returned to the client in JSON format. The client renders the data after getting it. The code is as follows ：

header('Content-Type:application/json; charset=utf-8');
$arr = array();
while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
    $arr[] = $row;
}
echo json_encode($arr);

The above code uses the mysqli_fetch_array() function to get data from $result, uses the array() function to save the data in the $arr array, encodes the array into JSON format, and uses echo to output to the client. .

5. Upload the PHP file to the server

Finally, upload the written "refresh.php" file to the specified path of the server.

3. The use of pull-down refresh in WeChat mini programs

In WeChat mini programs, using the pull-down refresh function requires the use of the officially provided API: onPullDownRefresh(). Call the onPullDownRefresh() function in the js file of the page. The code is as follows:

Page({
  onPullDownRefresh: function() {
    wx.request({
      url: 'http://www.example.com/refresh.php',
      success: function(res) {
        console.log(res.data);
        wx.stopPullDownRefresh(); //数据请求成功后结束刷新
        //将数据渲染到页面上
      }
    })
  }
})

In the above code, the onPullDownRefresh() function sends an HTTP request to the server through the wx.request() function. When the server returns the data , use the console.log() function to print the data on the console, and use the wx.stopPullDownRefresh() function to end the refresh.

Use the above code to implement the pull-down refresh function in the WeChat applet.

Summary

This article briefly introduces the method of using PHP to implement the pull-down refresh function in WeChat applet. By using PHP language to connect to the database and obtain the latest data and return it to the client in JSON format, Implemented pull-down refresh function. If you are a PHP developer and want to develop WeChat mini programs, the above methods are for reference.

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