(PHP 4, PHP 5, PHP 7)
md5 — 计算字符串的 MD5 散列值
It is not recommended to use this function to secure passwords, due to the fast nature of this hashing algorithm. See the Password Hashing FAQ for details and best practices.
$str
[, bool $raw_output = false
] )
使用 » RSA 数据安全公司的 MD5 报文算法计算 str 的 MD5 散列值。
str原始字符串。
raw_output
如果可选的 raw_output 被设置为 TRUE，那么 MD5 报文摘要将以16字节长度的原始二进制格式返回。
以 32 字符十六进制数字形式返回散列值。
Example #1 md5() 范例
<?php
$str = 'apple';
if (md5($str) === '1f3870be274f6c49b3e31a0c6728957f') {
echo "Would you like a green or red apple?";
}
?>
Note: Before you get some idea like using md5 with password as way to prevent others tampering with message, read pages "Length extension attack" and "Hash-based message authentication code" on wikipedia. In short, naive constructions can be dangerously insecure. Use hash_hmac if available or reimplement HMAC properly without shortcuts.
speed of hash('md5',) VS md5()
2017-07-14, on a i7-3540M CPU @ 3.00GHz, md5() is slightly quicker than hash('md5',)
This code takes 2.29 seconds
<?php
for($i=0;$i<10000000;++$i) md5("$i");
?>
while this one takes 2.77 seconds
<?php
for($i=0;$i<10000000;++$i) hash('md5',"$i");
?>
But in average, less than half a second for 10 000 000 repetitions is a very minimal advantage.
<?php
function raw2hex($rawBinaryChars)
{
return = array_pop(unpack('H*', $rawBinaryChars));
}
?>
The complement of hey2raw.
You can use to convert from raw md5-format to human-readable format.
This can be usefull to check "Content-Md5" HTTP-Header.
<?php
$rawMd5 = base64_decode($_SERVER['HTTP_CONTENT_MD5']);
$post_data = file_get_contents("php://input");
if(raw2hex($rawMd5) == md5($post_data)) // Post-Data is okay
else // Post-Data is currupted
?>
This recursive function allow you to hash something in depth using md5().
<?php
function checksum($what, $depth = 1) {
$depth--;
if (!$depth)
return md5($what);
else
return md5(checksum($what, $depth));
}
?>
The function hashed the previous hash to md5() again and again for number of times and returns the last received hash.
Example usage:
<?php
for ($i = 1; $i <= 10; $i++) {
echo "$i. ".checksum("test", $i)."<br />";
}
?>
It can be used for security purposes.
This is not encryption..... it's only a sort of DIGEST
If you want to hash a large amount of data you can use the hash_init/hash_update/hash_final functions.
This allows you to hash chunks/parts/incremental or whatever you like to call it.
MySQL MD() will not give you the same hash if character set is different.
ex :
<?php
#suppose table_name CHARSET=UTF8
#$md5 = md5('St?dte'); # will give you a different hash than MySQL MD5()
#instead use
$md5 = md5(utf8_encode('St?dte'));
$r = mysql_query("SELECT *, MD5(`word`) FROM `table_name` WHERE MD5(`word`) LIKE '{$md5}'");
if($r)
while( $row= mysql_fetch_assoc($r) )
print_r($row);
?>
Sometimes it's useful to get the actual, binary, md5 digest.
You can use this function for it:
<?php
function md5bin( $target ) {
$md5 = md5( $target );
$ret = '';
for ( $i = 0; $i < 32; $i += 2 ) {
$ret .= chr( hexdec( $md5{ $i + 1 } ) + hexdec( $md5{ $i } ) * 16 );
}
return $ret;
}
?>
It has been found, that hash('md5', 'string'); is faster than md5($string):
http://www.php.net/manual/en/function.hash.php
The complement of raw2hex
<?php
function hex2raw( $str ){
$chunks = str_split($str, 2);
for( $i = 0; $i < sizeof($chunks); $i++ ) {
$op .= chr( hexdec( $chunks[$i] ) );
}
return $op;
}
?>
Do not use the hex strings returned by md5() as a key for MCrypt 256-bit encryption. Hex characters only represent four bits each, so when you take 32 hex characters, you are only really using a 128-bit key, not a 256-bit one.
Using an alphanumeric key generator [A-Za-z0-9] will also only provide a 192-bit key in 32 characters.
Two different MD5s concatenated in raw binary form, or mcrypt_create_iv(32,MCRYPT_DEV_RANDOM) will give you a true 256-bit key string.
If you want to replicate CPAN Digest::MD5's function md5_base64 in PHP, use this code:
<?php
function md5_base64 ( $data )
{
return preg_replace('/=+$/','',base64_encode(pack('H*',md5($data))));
}
?>
From the documentation on Digest::MD5:
md5($data,...)
This function will concatenate all arguments, calculate the MD5 digest of this "message", and return it in binary form.
md5_hex($data,...)
Same as md5(), but will return the digest in hexadecimal form.
PHP's function returns the digest in hexadecimal form, so my guess is that you're using md5() instead of md5_hex(). I have verified that md5_hex() generates the same string as PHP's md5() function.
(original comment snipped in various places)
>Hexidecimal hashes generated with Perl's Digest::MD5 module WILL
>NOT equal hashes generated with php's md5() function if the input
>text contains any non-alphanumeric characters.
>
>$phphash = md5('pa$$');
>echo "php original hash from text: $phphash";
>echo "md5 hash from perl: " . $myrow['password'];
>
>outputs:
>
>php original hash from text: 0aed5d740d7fab4201e885019a36eace
>hash from perl: c18c9c57cb3658a50de06491a70b75cd