简述php对文件进行hash运算

本文实例讲述了php对文件进行hash运算的方法。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  button quot;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 

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