提升体验：PHP 异步 HTTP 下载多个文件的用户界面开发指南

$ php -m | grep curl

$ sudo apt-get install php-curl

<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>

<?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
?>

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

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();