php安全下载大文件的实现代码

2. /**
3. * 一般文件安全下载
4. * edit bbs.it-home.org
5. */
6. $durl = 'file/phpcms2008_o2abf32efj883c91a.iso';
7. $filename = 'phpcms2008_o2abf32efj883c91a.iso';
8. $file = @fopen($durl, 'r');
9. header("Content-Type: application/octet-stream");
10. header("Accept-Ranges: bytes");
11. header("Accept-Length: ".filesize($durl));
12. header("Content-Disposition: attachment; filename=".$filename);
13. echo fread($file,filesize($durl));
14. fclose($file);
15. ?>

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以上的代码，在遇到大文件时，超过php.ini配置的内存最大值的文件时，服务器会非常占用CPU资源，文件不能正常下载，只能下载几十Kb的文件。 可以用下面的代码来解决：

2. /**
3. * 大文件安全下载的实现代码
4. * edit bbs.it-home.org
5. */
6. function download($url, $filename) {
7. // 获得文件大小, 防止超过2G的文件, 用sprintf来读
8. $filesize = sprintf ( "%u", filesize ( $url ) );
9. if (! $filesize) {
10. return;
11. }
12. header ( "Content-type:application/octet-stream\n" ); //application/octet-stream
13. header ( "Content-type:unknown/unknown;" );
14. header ( "Content-disposition: attachment; filename=\"" . $filename . "\"" );
15. header ( 'Content-transfer-encoding: binary' );
16. if ($range = getenv ( 'HTTP_RANGE' )) { // 当有偏移量的时候，采用206的断点续传头
17. $range = explode ( '=', $range );
18. $range = $range [1];
20. header ( "HTTP/1.1 206 Partial Content" );
21. header ( "Date: " . gmdate ( "D, d M Y H:i:s" ) . " GMT" );
22. header ( "Last-Modified: " . gmdate ( "D, d M Y H:i:s", filemtime ( $url ) ) . " GMT" );
23. header ( "Accept-Ranges: bytes" );
24. header ( "Content-Length:" . ($filesize - $range) );
25. header ( "Content-Range: bytes " . $range . ($filesize - 1) . "/" . $filesize );
26. header ( "Connection: close" . "\n\n" );
27. } else {
28. header ( "Content-Length:" . $filesize . "\n\n" );
29. $range = 0;
30. }
31. loadFile ( $url );
32. }
34. function loadFile($filename, $retbytes = true) {
35. $buffer = '';
36. $cnt = 0;
37. $handle = fopen ( $filename, 'rb' );
38. if ($handle === false) {
39. return false;
40. }
41. while ( ! feof ( $handle ) ) {
42. $buffer = fread ( $handle, 1024 * 1024 );
43. echo $buffer;
44. ob_flush ();
45. flush ();
46. if ($retbytes) {
47. $cnt += strlen ( $buffer );
48. }
49. }
50. $status = fclose ( $handle );
51. if ($retbytes && $status) {
52. return $cnt; // return num. bytes delivered like readfile() does.
53. }
54. return $status;
55. }
56. ?>

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调用示例：

2. //大文件的安全下载
3. download($url, $filename);

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