使用 PHP 下载脚本发送正确的文件大小

问题描述

我用 PHP 创建了一个文件下载脚本，它可以工作，但网络浏览器将文件报告为未知长度".我的代码如下:

I created a file download script in PHP, it works, but web browsers report the file as "Unknown Length". My code is as follows:

function downloadFile($file){
  // Set up the download system...
  header('Content-Description: File Transfer');
  header('Content-Type: '.mime_content_type($file));
  header('Content-Disposition: attachment; filename="'.basename($file).'"');
  header('Content-Transfer-Encoding: binary');
  header('Expires: 0');
  header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
  header('Pragma: public');
  header('Content-Length: '.filesize($file));

  // Flush the cache
  ob_clean();
  flush();

  // Send file to browser
  readfile($file);

  // DO NOT DO ANYTHING AFTER FILE DOWNLOAD
  exit;
}

推荐答案

原文来自 http://paul.luminos.nl/update/471:

CrimsonBase 网站通过一个强大的 PHP 脚本来验证下载，类似于 Andrew Johnson 发布的脚本在 他关于 PHP 控制的文件下载的文章中.

The CrimsonBase website verifies downloads by passing them through a robust PHP script similar to the one published by Andrew Johnson in his article about PHP-controlled file downloads.

Andrew 在文章末尾发表了一个非常重要的评论:

Andrew makes a very important comment at the end of the article:

"如果您使用 Zlib、mod_deflate 等压缩文件，则 Content-Length 标头将不准确，因此您最终会看到未知大小"和剩余时间未知"下载文件时."

"If you compress files with Zlib, mod_deflate and so on the Content-Length header won't be accurate so you'll end up seeing "Unknown size" and "Unknown time remaining" when downloading files."

我想强调一点:如果您的浏览器似乎没有遵守由您的 PHP 脚本生成的标头——尤其是 Content-Length——很可能是 Apache 的 mod_deflate 扩展已启用.

I would like to stress this: if your browser doesn't appear to be obeying the headers generated by your PHP script—especially Content-Length—it is fairly likely that Apache's mod_deflate extension is enabled.

您可以使用适用的 .htaccess 文件中的以下行轻松为单个脚本禁用它:

You can easily disable it for a single script using the following line in an applicable .htaccess file:

SetEnvIfNoCase Request_URI ^/download.php no-gzip dont-vary

此处假定 download.php 位于服务器根目录路径中的下载脚本中(例如 www.crimsonbase.com/download.php).(那是因为正则表达式是^/download.php.)

where download.php is here assumed to be in the download script located in the server's root directory path (e.g. www.crimsonbase.com/download.php). (That's because the regular expression is ^/download.php.)

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