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。
<html> <head> <title>Hash (Check) Files</title> <style type='text/css'> #ok{color:green;} #nono{color:red;} </style> </head> <body> <?php if(!empty($_FILES)){ if ($_FILES["file"]["error"] > 0){ switch($_FILES["file"]["error"]){ case 1: echo "<b>Error: The uploaded file exceeds the upload_max_filesize directive in php.ini</b><br>"; break; case 2: echo "<b>Error: The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.</b><br>"; break; case 3: echo "<b>Error: The uploaded file was only partially uploaded.</b><br>"; break; case 4: echo "<b>Error: No file was uploaded.</b><br>"; break; case 6: echo "<b>Error: Missing a temporary folder.</b><br>"; break; case 7: echo "<b>Error: Failed to write file to disk.</b><br>"; break; case 8: echo "<b>Error: A PHP extension stopped the file upload.</b><br>"; break; default: echo "<b>Unknown error occured.</b><br>"; } } else { echo 'Upload: ' . $_FILES['file']['name'] . '<br>'; echo 'Type: ' . $_FILES['file']['type'] . '<br>'; echo 'Size: ' . (round($_FILES['file']['size'] / 1024, 2)) . ' Kb<br><br>'; if(array_search($_POST['algo'], hash_algos())===false){ echo 'Unknown hashing algorithm requested.<br>'; } else { echo 'Hashing Algorithm: '. $_POST['algo'] . '<br>'; $hash = hash_file($_POST['algo'], $_FILES['file']['tmp_name']); echo 'Calculated hash: ' . $hash . '<br>'; if($_POST['exphash']!=='none' && !empty($_POST['exphash'])){ echo 'Expected hash: ' . $_POST['exphash'] . '<br><br>'; echo ($hash==$_POST['exphash'])? '<b>Hash matched expected value.</b>' : '<b>Hash did not match expected value.</b>'; echo '<br>'; } } } ?> <br> <button>Again</button> <?php } else { ?> <form action="" method="post" enctype="multipart/form-data"> <input type="hidden" value="none"> <label for="file">Filename:</label> <input type="file"> <input type="submit" value="Submit" /><br> <label>Expected hash(optional): <input type="text" size="100"></label> <br><br>Choose an algorithm (This is the list of all the available algorithms in your php installation)<br> <?php foreach(hash_algos() as $algo){ if($algo=='md5'){ echo "<label><input type='radio' value='$algo' checked='checked'>$algo</label><br>"; } else { echo "<label><input type='radio' value='$algo'>$algo</label><br>"; } } ?> </form> <?php } ?> </body> </html>