md5_file

(PHP 4 >= 4.2.0, PHP 5)

md5_file — 计算指定文件的 MD5 散列值

说明

string md5_file ( string $filename [, bool $raw_output = false ] )

使用 » RSA 数据安全公司的 MD5 报文算法计算 filename 文件的 MD5 散列值并返回。该散列值为 32 字符的十六进制数字。

参数

filename: 文件名
raw_output: 如果被设置为 TRUE ，那么报文摘要将以原始的 16 位二进制格式返回。

返回值

成功返回字符串，否则返回 FALSE 。

更新日志

版本	说明
5.1.0	函数改用流 API。这意味着能够配合封装器使用该函数，比如 md5_file('http://example.com/..')。

范例

Example #1 md5_file() 使用范例

  <?php
$file  =  'php-5.3.0alpha2-Win32-VC9-x64.zip' ;

echo  'MD5 file hash of '  .  $file  .  ': '  .  md5_file ( $file );
 ?>

参见

md5() - 计算字符串的 MD5 散列值
sha1_file() - 计算文件的 sha1 散列值
crc32() - 计算一个字符串的 crc32 多项式

用户评论:

[#1] tommuhler at yahoo dot com [2013-11-20 16:10:38]

Sorry for voting Chris's code down.

It is great, but there are some brackets missing. If you add more complex conditions than just a mere echo in the top IF ... ELSE structure please include the curly braces ... otherwise php will choke.

<?php define('READ_LEN', 4096); if(files_identical('file1.txt', 'file2.txt')) { echo 'files identical'; } else { echo 'files not identical'; } // pass two file names // returns TRUE if files are the same, FALSE otherwise function files_identical($fn1, $fn2) { if(filetype($fn1) !== filetype($fn2)) return FALSE; if(filesize($fn1) !== filesize($fn2)) return FALSE; if(!$fp1 = fopen($fn1, 'rb')) return FALSE; if(!$fp2 = fopen($fn2, 'rb')) { fclose($fp1); return FALSE; } $same = TRUE; while (!feof($fp1) and !feof($fp2)) if(fread($fp1, READ_LEN) !== fread($fp2, READ_LEN)) { $same = FALSE; break; } if(feof($fp1) !== feof($fp2)) $same = FALSE; fclose($fp1); fclose($fp2); return $same; } ?>

[#2] lukasamd at gmail dot com [2012-02-14 10:35:16]

It's faster to use md5sum than openssl md5:

<?php $begin = microtime(true); $file_path = '../backup_file1.tar.gz'; $result = explode(" ", exec("md5sum $file_path")); echo "Hash = ".$result[0]."<br />"; # Here 7 other big files (20-300 MB) $end = microtime(true) - $begin; echo "Time = $end"; # Time = 4.4475841522217 #Method with openssl # Time = 12.1463856900543 ?>

About 3x faster

[#3] Chris [2009-11-08 07:24:03]

If you just need to find out if two files are identical, comparing file hashes can be inefficient, especially on large files. There's no reason to read two whole files and do all the math if the second byte of each file is different. If you don't need to store the hash value for later use, there may not be a need to calculate the hash value just to compare files. This can be much faster:

<?php define('READ_LEN', 4096); if(files_identical('file1.txt', 'file2.txt')) echo 'files identical'; else echo 'files not identical'; // pass two file names // returns TRUE if files are the same, FALSE otherwise function files_identical($fn1, $fn2) { if(filetype($fn1) !== filetype($fn2)) return FALSE; if(filesize($fn1) !== filesize($fn2)) return FALSE; if(!$fp1 = fopen($fn1, 'rb')) return FALSE; if(!$fp2 = fopen($fn2, 'rb')) { fclose($fp1); return FALSE; } $same = TRUE; while (!feof($fp1) and !feof($fp2)) if(fread($fp1, READ_LEN) !== fread($fp2, READ_LEN)) { $same = FALSE; break; } if(feof($fp1) !== feof($fp2)) $same = FALSE; fclose($fp1); fclose($fp2); return $same; } ?>

[#4] smartin [2008-03-12 04:58:42]

In response to using exec instead for performance (Nov 13 2007 post), It looks like the performance depends on the size of the file. See the results below using the same script from the original post. The first hash is with md5_file and the second is with openssl md5.

With a 1MB file:
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.005006
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.01498

With a 2MB file:

Hash = 4387904830a4245a8ab767e5937d722c; time = 0.010393
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.016691

With a 10MB file:

Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.241907
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.037597

Performance seems to change proportionally with the file size. Judging from the previous post's default file name (.mov) he/she was probably dealing with a large file. These are just quick tests and far from a perfect benchmark, but you might want to test your own files before assuming that the openssl solution is faster (ie, if working with small text files vs. movies, etc)

[#5] potsed [at] gmail [dot] com [2007-05-27 04:12:11]

Heres a function to give an md5 for an entire directory..

function MD5_DIR($dir)
{
    if (!is_dir($dir))
    {
        return false;
    }

    $filemd5s = array();
    $d = dir($dir);

    while (false !== ($entry = $d->read()))
    {
        if ($entry != '.' && $entry != '..')
        {
             if (is_dir($dir.'/'.$entry))
             {
                 $filemd5s[] = MD5_DIR($dir.'/'.$entry);
             }
             else
             {
                 $filemd5s[] = md5_file($dir.'/'.$entry);
             }
         }
    }
    $d->close();
    return md5(implode('', $filemd5s));
}

[#6] richard at interlink dot com dot au [2004-11-16 00:57:34]

For those of you with PHP 4 that want to output the "raw" 128 bit hash, all you need to do is send it to pack to convert the hex string into the raw output.

ie:
$filename="checkthisfile.bin";
$rawhash=pack("H*",md5_file($filename));