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php实现下载功能

2026-04-03 01:10:31PHP

PHP 实现下载功能的方法

直接文件下载
通过设置 HTTP 头部强制浏览器下载文件而非直接打开：

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

动态生成内容下载
适用于需要将字符串或动态生成的内容作为文件提供下载：

$content = "This will be saved in the downloaded file.";
header('Content-Type: text/plain');
header('Content-Disposition: attachment; filename="data.txt"');
echo $content;
exit;

大文件分块下载
处理大文件时避免内存溢出：

$file = 'large_video.mp4';
$chunk_size = 1024 * 1024; // 1MB per chunk

$handle = fopen($file, 'rb');
header('Content-Type: video/mp4');
header('Content-Disposition: attachment; filename="' . basename($file) . '"');

while (!feof($handle)) {
    echo fread($handle, $chunk_size);
    ob_flush();
    flush();
}
fclose($handle);
exit;

安全下载注意事项

验证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'); }


常见 MIME 类型对照  
根据文件类型自动设置正确的 Content-Type：
```php
$mime_types = [
    'txt' => 'text/plain',
    'pdf' => 'application/pdf',
    'jpg' => 'image/jpeg',
    'png' => 'image/png'
];

$ext = strtolower(pathinfo($file_path, PATHINFO_EXTENSION));
header('Content-Type: ' . ($mime_types[$ext] ?? 'application/octet-stream'));

断点续传支持
实现 HTTP 范围请求（Range Requests）：

php实现下载功能

if (isset($_SERVER['HTTP_RANGE'])) {
    $size = filesize($file_path);
    list(, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
    list($start, $end) = explode('-', $range, 2);

    $start = max(0, (int)$start);
    $end = min($size - 1, empty($end) ? ($size - 1) : (int)$end);

    header('HTTP/1.1 206 Partial Content');
    header('Content-Range: bytes ' . $start . '-' . $end . '/' . $size);
    header('Content-Length: ' . ($end - $start + 1));

    $fp = fopen($file_path, 'rb');
    fseek($fp, $start);
    echo fread($fp, $end - $start + 1);
    fclose($fp);
}

以上方法涵盖了从基础文件下载到高级功能的实现，开发者可根据实际需求选择适合的方案。