Master the actual combat: PHP asynchronous HTTP development examples and solutions for downloading multiple files

Master the actual combat: PHP asynchronous HTTP development examples and solutions for downloading multiple files

Introduction:
In the development process, we often need to download multiple files from the Internet Download large amounts of files such as pictures, documents, etc. The traditional download method is to download in a synchronous manner, which means that the next file can only be downloaded after one file is downloaded, which will cause the download speed to be slower and the user experience to be poor. Asynchronous downloading can download multiple files at the same time, improving download speed and user experience. This article will introduce development examples and solutions on how to use PHP asynchronous HTTP to download multiple files.

1. Background knowledge

1. PHP environment: The example in this article is developed based on the PHP environment, so PHP needs to be installed on the server and ensure that the PHP version is greater than or equal to 5.2.0 .
2. Asynchronous request library: In PHP, we can use cURL to make asynchronous HTTP requests, so we need to ensure that the cURL library has been installed on the server.

2. Development Example
The following is a simple PHP development example for asynchronous downloading of multiple files:

<?php

$urls = array(
    'https://example.com/file1.jpg',
    'https://example.com/file2.jpg',
    'https://example.com/file3.jpg',
    // 更多文件的 URL
);

$curlHandles = array();
$result = array();

// 初始化 cURL
$multiHandle = curl_multi_init();

foreach ($urls as $index => $url) {
    $curlHandle = curl_init($url);
    
    // 设置 cURL 选项
    curl_setopt($curlHandle, CURLOPT_RETURNTRANSFER, true);
    
    // 添加到多个句柄中
    curl_multi_add_handle($multiHandle, $curlHandle);
    
    $curlHandles[$index] = $curlHandle;
}

// 执行并发请求
do {
    $status = curl_multi_exec($multiHandle, $runningHandles);
} while ($status === CURLM_CALL_MULTI_PERFORM || $runningHandles);

// 处理结果
foreach ($curlHandles as $index => $curlHandle) {
    // 检查请求是否成功
    $error = curl_error($curlHandle);
    if ($error) {
        $result[$index] = array(
            'success' => false,
            'error' => $error,
        );
    } else {
        // 获取响应内容
        $response = curl_multi_getcontent($curlHandle);
        
        // 保存文件，此处省略
        // file_put_contents('path/to/save/file', $response);
        
        $result[$index] = array(
            'success' => true,
            'file' => 'path/to/save/file',
        );
    }
    
    // 移除句柄
    curl_multi_remove_handle($multiHandle, $curlHandle);
}

// 关闭多个句柄
curl_multi_close($multiHandle);

// 输出结果
var_dump($result);

?>

3. Solution
In the development of asynchronous downloading of multiple files When writing files, we may encounter some common problems. Here are some solutions:

1. Concurrency limit: Due to the limited resources of the server, too many concurrent requests at the same time may cause the server to crash. or performance degradation. In order to avoid this problem, we can set an upper limit on the number of concurrent requests. Requests exceeding this upper limit need to wait for the previous request to complete before continuing.
2. Error handling: Due to network instability, some download failures may occur. In order to improve the success rate of downloading, we can set the number of retries and give up the download when the number of retries reaches the upper limit.
3. File saving: Downloaded files can be saved to a local server or other storage methods, select according to actual needs.

Conclusion:
Through the examples and solutions in this article, we learned how to use PHP asynchronous HTTP to download multiple files and solved some common problems. Asynchronous downloading can significantly improve download speed and user experience, and is worth mastering and applying in project development. Hope this article is helpful to everyone.

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