限制文件下载速度php代码

如下代码实现php限制下载速度：

1. /* Source: http://www.apphp.com/index.php?snippet=php-download-file-with-speed-limit */
2. /* set here a limit of downloading rate (e.g. 10.20 Kb/s) */
3. $download_rate = 10.20;
5. $download_file = 'download-file.zip';
6. $target_file = 'target-file.zip';
8. if(file_exists($download_file)){
9. /* headers */
10. header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT');
11. header('Cache-control: private');
12. header('Content-Type: application/octet-stream');
13. header('Content-Length: '.filesize($download_file));
14. header('Content-Disposition: filename='.$target_file);
16. /* flush content */
17. flush();
19. /* open file */
20. $fh = @fopen($download_file, 'r');
21. while(!feof($fh)){
22. /* send only current part of the file to browser */
23. print fread($fh, round($download_rate * 1024));
24. /* flush the content to the browser */
25. flush();
26. /* sleep for 1 sec */
27. sleep(1);
28. }
29. /* close file */
30. @fclose($fh);
31. }else{
32. die('Fatal error: the '.$download_file.' file does not exist!');
33. }
34. ?>