Php 简明教程

PHP - AJAX Introduction

由 PHP 提供支持的 Web 应用程序通常使用 AJAX，两者联合起来可用来创建动态且交互式的 Web 应用程序。AJAX 代表 Asynchronous Javascript and XML 。它允许网页异步更新，而无需重新加载整个页面。

PHP powered web applications often make use of AJAX, together they are useful to create dynamic and interactive web applications. AJAX stands for Asynchronous Javascript and XML. It allows webpages to be updated asynchronously without reloading the entire page.

在 AJAX 应用程序中，Web 浏览器与服务器端 PHP 脚本之间的数据交换是异步的。PHP 是一种服务器端脚本语言，可用于生成动态内容并处理数据。

In AJAX applications, the exchange of data between a web browser and the server-side PHP script is asynchronous. PHP is a server-side scripting language that can be used to generate dynamic content and process data.

由于我们可以使用 JavaScript 执行后台服务器调用并检索所需数据，并且可以在不强制页面完全重新加载的情况下更新网页的请求部分，所以 AJAX 在 Web 应用程序与 Web 服务器之间创建了一层附加层（称为 AJAX 引擎）。它缩短了页面刷新时间，并且为用户提供了迅速而灵敏的体验。

AJAX creates an additional layer known as AJAX engine in between the web application and web server due to which we can make background server calls using JavaScript and retrieve the required data, can update the requested portion of a web page without casing full reload of the page. It reduces the page refresh timing and provides a fast and responsive experience to the user.

php ajax introduction

What is Required to Run AJAX?

AJAX 使用的技术已经在所有现代浏览器中实现。因此，客户端不需要任何额外的模块来运行 AJAX 应用程序。AJAX 使用的技术有 −

The technologies that are used by AJAX are already implemented in all the Morden browsers. So the client does not require any extra module to run the AJAX application. The technologies used by AJAX are −

  1. Javascript − It is an important part of AJAX. It allows you to create client-side functionality. Or we can say that it is used to create AJAX applications.

  2. XML − It is used to exchange data between web server and client.

  3. The XMLHttpRequest − It is used to perform asynchronous data exchange between a web browser and a web server.

  4. HTML and CSS − It is used to provide markup and style to the webpage text.

  5. DOM − It is used to interact with and alter the webpage layout and content dynamically.

在 PHP 中使用 AJAX，将需要使用 JavaScript 中的 XMLHttpRequest 对象向 PHP 服务器发送请求。然后 PHP 服务器将处理请求并返回响应，通常以 JSON 或 XML 的形式。随后 JavaScript 代码能够分析响应并相应地更新网页。

To use AJAX with PHP, you will need to use the XMLHttpRequest object in JavaScript to send requests to the PHP server. The PHP server will then process the request and return a response, typically in the form of JSON or XML. The JavaScript code can then parse the response and update the web page accordingly.

JavaScript 中的 XMLHttpRequest 对象是基于浏览器的 API，允许开发者向服务器发出 HTTP 请求而无需刷新该页面。这是 AJAX 编程的基础，这允许动态且互动的 Web 应用。

The XMLHttpRequest object in JavaScript is a browser-based API that allows developers to make HTTP requests to a server without reloading the page. This is the foundation of AJAX programming, which allows for dynamic and interactive web applications.

XMLHttpRequest 对象可以用来 −

The XMLHttpRequest object can be used to −

  1. Retrieve data from a server, such as JSON, XML, or HTML.

  2. Send data to a server, such as form data or file uploads.

  3. Update a web page without reloading it.

  4. Create chat applications and other interactive features.

要使用 XMLHttpRequest 对象，首先需要创建一个新实例。然后，可以使用 open() 方法指定 HTTP 方法和请求 URL。下一步，可以设置任何请求头（如果需要的话）。最后，可以使用 send() 方法发送请求。

To use the XMLHttpRequest object, you first need to create a new instance of it. Then, you can use the open() method to specify the HTTP method and request URL. Next, you can set any request headers, if needed. Finally, you can send the request using the send() method.

Example

以下是如何使用 XMLHttpRequest 对象从服务器检索数据的简单 JavaScript 代码 −

Here is a simple JavaScript code of how to use the XMLHttpRequest object to retrieve data from a server −

// Create a new XMLHttpRequest object
var xhr = new XMLHttpRequest();

// Set the HTTP method and request URL
xhr.open("GET", "test.php");

// Send the request
xhr.send();

// Listen for the onload event to be fired
xhr.onload = function() {

   // Check the status code to ensure the request was successful
   if (xhr.status === 200) {

      // Get the response data.
      var users = JSON.parse(xhr.responseText);

      // Do something with the user data.
   } else {
      // Handle the error
   }
};

服务器上的 PHP 脚本从 AJAX 请求中检索数据并发送回响应。

The PHP script on the server retrieves the data from AJAX request and sends back the response.

// Get the request data.
$name = $_GET["name"];

// Create a response object.
$response = new stdClass();
$response->message = "Hello, $name!";

// Send the response back to the client.
header("Content-Type: application/json");
echo json_encode($response);