How to get variables from PHP method using Ajax?

Using Ajax to obtain variables from PHP methods is a common scenario in web development. Through Ajax, the page can be dynamically obtained without refreshing the data. In this article, we will introduce how to use Ajax to get variables from PHP methods, and provide specific code examples.

First, we need to write a PHP file to handle the Ajax request and return the required variables. The following is a sample code for a simple PHP file getData.php:

<?php
    // 获取传递进来的参数
    $param = $_POST['param'];

    // 执行一些操作，比如从数据库中获取数据
    $result = fetchDataFromDatabase($param);

    // 返回结果
    echo json_encode($result);

    // 从数据库获取数据的函数示例
    function fetchDataFromDatabase($param) {
        // 连接数据库
        $conn = new mysqli('localhost', 'username', 'password', 'database');

        // 执行查询
        $query = "SELECT * FROM table WHERE column = '$param'";
        $result = $conn->query($query);

        // 处理查询结果
        $data = array();
        while($row = $result->fetch_assoc()) {
            $data[] = $row;
        }

        // 关闭数据库连接
        $conn->close();

        return $data;
    }
?>

Next, we need to write JavaScript code in the front-end page to send an Ajax request and obtain the variables in the PHP method . The following is a simple sample code:

// 创建一个XMLHttpRequest对象
var xhr = new XMLHttpRequest();

// 设置Ajax请求的方法、URL和是否异步
xhr.open('POST', 'getData.php', true);

// 设置请求头信息
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');

// 监听Ajax请求的状态变化
xhr.onreadystatechange = function() {
    if(xhr.readyState == 4 && xhr.status == 200) {
        // 获取PHP返回的数据
        var data = JSON.parse(xhr.responseText);

        // 处理获取到的数据
        processData(data);
    }
};

// 发送Ajax请求
xhr.send('param=value');

In the above code, an XMLHttpRequest object is first created, and the request method, URL and whether it is asynchronous are set. Then in the status change event of the request, determine whether the request is successful and obtain the returned data, and finally process the obtained data. It should be noted that parameters need to be passed when sending a request, and parameters can be passed through the xhr.send() method.

In summary, through the above code examples, you can use Ajax to obtain variables from PHP methods. The front-end page sends an Ajax request to the back-end PHP file, and the back-end PHP file performs corresponding operations and returns data. The front-end page then processes the returned data, achieving the effect of obtaining data without refreshing the page.

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