Improving experience: User interface development guide for PHP asynchronous HTTP download of multiple files

Improve experience: User interface development guide for PHP asynchronous HTTP downloading multiple files

Introduction:
In modern web applications, file downloading is very common One of the functions. However, when multiple files need to be downloaded, the traditional synchronous download method may cause users to wait too long. In order to improve the user experience, we can use PHP's asynchronous HTTP request function to achieve concurrent downloading of multiple files. This article will provide you with a detailed guide to help you develop an asynchronous download function with a good user interface.

1. Understanding Asynchronous HTTP Download
Traditional synchronous HTTP download downloads files one by one in sequence, while asynchronous HTTP download initiates multiple HTTP requests at the same time and downloads multiple files in parallel. This can greatly reduce the waiting time of users and improve download speed and user experience.

2. Preparation
Before starting development, we need to ensure that your PHP environment has the cURL extension installed. You can check whether it is installed by running the following command:

$ php -m | grep curl

If the curl extension name is not displayed, it needs to be installed. On Ubuntu systems, you can use the following command to install:

$ sudo apt-get install php-curl

3. Develop asynchronous download function

1. Create a download form:
   First, we need to provide an interface for users Select the file you want to download and submit a download request. A simple form can be created in HTML:

<form action="download.php" method="POST">
    <input type="checkbox" name="files[]" value="file1">
    <input type="checkbox" name="files[]" value="file2">
    <input type="checkbox" name="files[]" value="file3">
    <button type="submit">下载</button>
</form>

2. Create an asynchronous download processing script:
   Next, we need to create a PHP script to handle the download request. In the download.php file, we can use the curl_multi_init function to initialize a parallel processing curl conversation:

<?php
$files = $_POST['files']; // 获取用户选择的文件

$mh = curl_multi_init(); // 初始化curl多个句柄

foreach ($files as $file) {
    $ch = curl_init(); // 初始化curl句柄
    curl_setopt($ch, CURLOPT_URL, "http://example.com/files/$file"); // 设置要下载的文件URL
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // 设置返回结果为字符串
    curl_multi_add_handle($mh, $ch); // 添加curl句柄到并行处理中
}

do {
    $status = curl_multi_exec($mh, $running); // 执行并行处理
} while ($status === CURLM_CALL_MULTI_PERFORM || $running);

foreach ($files as $file) {
    $ch = curl_multi_getcontent($ch); // 获取文件内容
    file_put_contents($file, $content); // 将文件内容写入本地文件
    curl_multi_remove_handle($mh, $ch); // 移除curl句柄
}

curl_multi_close($mh); // 关闭curl多句柄
?>

3. Add an asynchronous download progress bar:
   In order to provide a better user experience , we can add a progress bar to the user interface to show the progress of each file download. This can be achieved using the progress element of HTML5:

<progress id="progress" value="0" max="100"></progress>

In JavaScript, we can use the XMLHttpRequest object to obtain the download progress and update the value of the progress bar:

var progress = document.getElementById('progress');

var xhr = new XMLHttpRequest();

xhr.addEventListener('progress', function(e) {
    if (e.lengthComputable) {
        var percent = (e.loaded / e.total) * 100;
        progress.value = percent;
    }
});

xhr.open('GET', 'download.php', true);
xhr.send();

4. Summary
By downloading multiple files asynchronously via PHP HTTP, we can greatly improve the user experience and speed up file downloads. During the development process, we need to ensure that the cURL extension has been installed in the PHP environment and follow the steps to create the download form, asynchronous download processing script and add download progress bar. With the development of web applications, improving user experience will become the focus of developers, and the asynchronous HTTP download function will become an important tool for you to achieve this goal. Let’s have fun creating better user interfaces!

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