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;
}
?>
md5_file
(PHP 4 >= 4.2.0, PHP 5, PHP 7)
md5_file — 주어진 파일의 md5 해시를 계산
설명
string md5_file
( string
$filename
[, bool $raw_output
] )
» RSA Data Security, Inc. MD5 Message-Digest
Algorithm을 사용해서 filename 인수로 지정한
파일의 MD5 해시를 계산해서 반환합니다. 해시는 32문자의 16진수입니다.
인수
-
filename -
파일명
-
raw_output -
TRUE이면, 해시를 길이 16의 바이너리 형식으로 반환합니다. 기본값은FALSE입니다.
반환값
성공시엔 문자열을, 그 외엔 FALSE를 반환합니다.
변경점
| 버전 | 설명 |
|---|---|
| 5.0.0 |
raw_output 인수 추가
|
| 5.1.0 | 스트림 API를 사용합니다. 즉, md5_file('http://example.com/..')처럼 래퍼를 사용할 수 있습니다. |
예제
Example #1 md5_file() 용례
<?php
$file = 'php-5.3.0alpha2-Win32-VC9-x64.zip';
echo 'MD5 file hash of ' . $file . ': ' . md5_file($file);
?>
add a note
User Contributed Notes 5 notes
Chris ¶
14 years ago
lukasamd at gmail dot com ¶
12 years ago
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 = $end";
# Time = 4.4475841522217
#Method with openssl
# Time = 12.1463856900543
?>
About 3x faster
smartin ¶
16 years ago
In response to using exec instead for performance (Nov 13 2007 post), It looks like the performance depends on the size of the file. See the results below using the same script from the original post. The first hash is with md5_file and the second is with openssl md5.
With a 1MB file:
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.005006
Hash = df1555ec0c2d7fcad3a03770f9aa238a; time = 0.01498
With a 2MB file:
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.010393
Hash = 4387904830a4245a8ab767e5937d722c; time = 0.016691
With a 10MB file:
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.241907
Hash = b89f948e98f3a113dc13fdbd3bdb17ef; time = 0.037597
Performance seems to change proportionally with the file size. Judging from the previous post's default file name (.mov) he/she was probably dealing with a large file. These are just quick tests and far from a perfect benchmark, but you might want to test your own files before assuming that the openssl solution is faster (ie, if working with small text files vs. movies, etc)
potsed [at] gmail [dot] com ¶
16 years ago
Heres a function to give an md5 for an entire directory..
function MD5_DIR($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));
}
richard at interlink dot com dot au ¶
19 years ago
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));
