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php怎么实现下载

2026-04-03 05:15:29PHP

实现文件下载的基本方法

使用PHP的header()函数设置HTTP头信息，结合readfile()函数输出文件内容。以下是一个简单示例：

$file_path = '/path/to/your/file.pdf';
$file_name = 'download.pdf';

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="'.basename($file_name).'"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . filesize($file_path));
readfile($file_path);
exit;

处理大文件下载

对于大文件，使用分块读取避免内存问题：

$chunk_size = 1024 * 1024; // 1MB chunks
$handle = fopen($file_path, 'rb');
while (!feof($handle)) {
    echo fread($handle, $chunk_size);
    ob_flush();
    flush();
}
fclose($handle);

安全下载控制

验证用户权限和文件路径，防止目录遍历攻击：

$base_dir = '/safe/directory/';
$requested_file = $_GET['file'];
$real_path = realpath($base_dir . $requested_file);

if (strpos($real_path, $base_dir) !== 0 || !file_exists($real_path)) {
    die('Invalid file');
}

断点续传支持

实现HTTP Range请求支持：

$size = filesize($file_path);
$start = 0;
$end = $size - 1;

if (isset($_SERVER['HTTP_RANGE'])) {
    if (preg_match('/bytes=(\d+)-(\d+)?/', $_SERVER['HTTP_RANGE'], $matches)) {
        $start = intval($matches[1]);
        if (!empty($matches[2])) {
            $end = intval($matches[2]);
        }
    }
    header('HTTP/1.1 206 Partial Content');
    header("Content-Range: bytes $start-$end/$size");
}

header("Accept-Ranges: bytes");
header("Content-Length: " . ($end - $start + 1));

强制下载特定MIME类型

设置特定的Content-Type强制浏览器下载：

$mime_types = [
    'pdf' => 'application/pdf',
    'zip' => 'application/zip',
    // 添加更多MIME类型
];

$ext = strtolower(pathinfo($file_path, PATHINFO_EXTENSION));
if (array_key_exists($ext, $mime_types)) {
    header('Content-Type: ' . $mime_types[$ext]);
}

下载进度监控

使用输出缓冲和回调函数监控下载进度：

php怎么实现下载

function readfile_chunked($filename, $chunk_size = 1024, $callback = null) {
    $handle = fopen($filename, 'rb');
    $total = filesize($filename);
    $sent = 0;

    while (!feof($handle)) {
        $buffer = fread($handle, $chunk_size);
        echo $buffer;
        $sent += strlen($buffer);
        if (is_callable($callback)) {
            call_user_func($callback, $sent, $total);
        }
        ob_flush();
        flush();
    }
    fclose($handle);
}

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