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php对文件进行hash运算的方法

　　本文标签：php,文件,hash运算

本文实例讲述了php对文件进行hash运算的方法 。分享给大家供大家参考 。具体如下：

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 id=nono>Error: The uploaded file exceeds the upload_max_filesize directive in php.ini</b><br>";
     break;
     case 2:
     echo "<b id=nono>Error: The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.</b><br>";
     break;
     case 3:
     echo "<b id=nono>Error: The uploaded file was only partially uploaded.</b><br>";
     break;
     case 4:
     echo "<b id=nono>Error: No file was uploaded.</b><br>";
     break;
     case 6:
     echo "<b id=nono>Error: Missing a temporary folder.</b><br>";
     break;
     case 7:
     echo "<b id=nono>Error: Failed to write file to disk.</b><br>";
     break;
     case 8:
     echo "<b id=nono>Error: A PHP extension stopped the file upload.</b><br>";
     break;
     default:
     echo "<b id=nono>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 id="ok">Hash matched expected value.</b> : <b id="nono">Hash did not match expected value.</b>;
      echo <br>;
    }
    }
   }
   ?>
   <br>
   <button onClick="document.location.reload(true)">Again</button>
    <?php
   } else {
  ?>
  <form action="" method="post" enctype="multipart/form-data">
   <input type="hidden" name="exphash" value="none">
   <label for="file">Filename:</label>
   <input type="file" name="file" id="file">
   <input type="submit" name="submit" value="Submit" /><br>
   <label>Expected hash(optional): <input type="text" name="exphash" 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 name=algo value=$algo checked=checked>$algo</label><br>";
    } else {
    echo "<label><input type=radio name=algo value=$algo>$algo</label><br>";
    }
   }
   ?>
  </form>
 <?php
   }
  ?>
</body>
</html>

希望本文所述对大家的php程序设计有所帮助 。