php控制文件下载速度

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

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下载速度, php