php对文件进行hash运算

这段代码非常有用，如果你下载了一个文件，网站提供了hash结果，你可以对你下载下来的文件进行hash运算，以验证下载的文件是否正确。

7. if(!empty($_FILES)){
8. if ($_FILES["file"]["error"] > 0){
9. switch($_FILES["file"]["error"]){
10. case 1:
11. echo "Error: The uploaded file exceeds the upload_max_filesize directive in php.ini
    ";
12. break;
13. case 2:
14. echo "Error: The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.
    ";
15. break;
16. case 3:
17. echo "Error: The uploaded file was only partially uploaded.
    ";
18. break;
19. case 4:
20. echo "Error: No file was uploaded.
    ";
21. break;
22. case 6:
23. echo "Error: Missing a temporary folder.
    ";
24. break;
25. case 7:
26. echo "Error: Failed to write file to disk.
    ";
27. break;
28. case 8:
29. echo "Error: A PHP extension stopped the file upload.
    ";
30. break;
31. default:
32. echo "Unknown error occured.
    ";
33. }
34. } else {
35. echo 'Upload: ' . $_FILES['file']['name'] . '
    ';
36. echo 'Type: ' . $_FILES['file']['type'] . '
    ';
37. echo 'Size: ' . (round($_FILES['file']['size'] / 1024, 2)) . ' Kb
    
    ';
38. if(array_search($_POST['algo'], hash_algos())===false){
39. echo 'Unknown hashing algorithm requested.
    ';
40. } else {
41. echo 'Hashing Algorithm: '. $_POST['algo'] . '
    ';
42. $hash = hash_file($_POST['algo'], $_FILES['file']['tmp_name']);
43. echo 'Calculated hash: ' . $hash . '
    ';
44. if($_POST['exphash']!=='none' && !empty($_POST['exphash'])){
45. echo 'Expected hash: ' . $_POST['exphash'] . '
    
    ';
46. echo ($hash==$_POST['exphash'])? 'Hash matched expected value.' : 'Hash did not match expected value.';
47. echo '
    ';
48. }
49. }
50. }
51. ?>
52. 
    
53. Again
54. } else {
55. ?>
57. }
58. ?>