How to combine PHP and Ajax to achieve refresh-free data update

With the popularity of web applications, users expect a more interactive user experience. Traditional web pages use synchronous requests (that is, refreshing the entire page) to update data, which often results in tedious waiting times. Ajax technology has become a commonly used asynchronous request method, which can refresh some pages and improve the user's interactive experience. Combining PHP and Ajax can more easily achieve refresh-free data updates. This article will introduce how to combine PHP and Ajax to achieve refresh-free data update.

1. What is Ajax?

Ajax refers to Asynchronous JavaScript and XML, which allows parts of the page to be updated without refreshing the entire page. By using the "XMLHttpRequest" object, JavaScript code can send an HTTP request to the server, and the server returns the data and then updates the data to the web page.

2. Refresh-free data update combining PHP and Ajax

1. Front-end code implementation

In the front-end code, we need to first use JavaScript " XMLHttpRequest" object to send HTTP requests. Then, after waiting for the server to respond, the corresponding web page is updated based on the response result.

The following is an Ajax sample code that can send a request to the update.php file:

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
        document.getElementById("result").innerHTML = this.responseText;
    }
};

xmlhttp.open("GET", "update.php?q=" + str, true);
xmlhttp.send();

In this example, when readyState is equal to 4 and status is equal to 200, it means that the request has been successful. return. The request result will be updated in the DOM element with the id "result".

2. Backend code implementation

In the backend code, we need to first determine whether the request method is GET or POST. Then update the data or return the data according to the requested parameters.

The following is a PHP code example that can be used to handle Ajax requests:

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // 更新数据
    $username = $_POST['username'];
    $password = $_POST['password'];
    // ...
} else if ($_SERVER["REQUEST_METHOD"] == "GET") {
    // 获取数据
    $q = $_REQUEST['q'];
    // ...
}
?>

In this example, when the request method is POST, the data is updated according to the parameters of the request; when the request method is When GET, data is returned according to the requested parameters.

3. Steps to implement refresh-free data update

The steps to implement refresh-free data update by combining PHP and Ajax are as follows:

1. Write front-end code and use JavaScript The "XMLHttpRequest" object sends HTTP requests.
2. Write back-end code to update data or return data according to the request method and parameters.
3. In the front-end code, update the web page based on the server response results.

4. How to optimize Ajax performance?

In the process of using Ajax, some performance issues also need to be considered to ensure application performance and user experience. Here are some suggestions for optimizing Ajax performance:

1. Use GET requests instead of POST requests. GET requests are faster than POST requests.
2. Minimize the size of Ajax requests. Try to avoid sending unnecessary data. You can use JSON data format, which is more compact.
3. Keep the wait time as short as possible before processing the AJAX response. This can be done by caching the data, or by preprocessing the data in the background. Before responding, consider using gzip to compress the response data on the server side to reduce the amount of data.
4. Avoid sending too many Ajax requests. Merge requests, send the request once, and process the data locally.

The above methods can not only improve the performance of Ajax, but also make our web applications more efficient.

Summary:

Combining PHP and Ajax to achieve refresh-free data updates can improve the user experience and performance of web applications. This article introduces how to write front-end and back-end code and how to optimize the performance of Ajax. With this knowledge, you can better use Ajax technology and improve the quality and performance of web applications.

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