PHP 7.1.18 Released


(PHP 4, PHP 5, PHP 7)

md5Calcula el 'hash' md5 de un string


No se recomienda utilizar esta función para contraseñas seguras debido a la naturaleza rápida de este algoritmo de «hashing». Véase las Preguntas más frecuentes de «hash» de contraseñas para más detalles y el empleo de mejores prácticas.


string md5 ( string $str [, bool $raw_output = false ] )

Calcula el hash MD5 de str utilizando el » Algoritmo MD5 Message-Digest de RSA Data Security, Inc. y devuelve ese hash.



El string.


Si se establece el raw_output opcional en TRUE, el resumen md5 será devuelto en formato binario sin tratar con una longitud de 16.

Valores devueltos

Devuelve el hash como un número hexadecimal de 32 caracteres.


Ejemplo #1 Ejemplo de md5()


if (
md5($str) === '1f3870be274f6c49b3e31a0c6728957f') {
"Would you like a green or red apple?";

Ver también

  • md5_file() - Calcula el resumen criptográfico md5 de un archivo dado
  • sha1_file() - Calcula el hash sha1 de un archivo
  • crc32() - Calcula el polinomio crc32 de una cadena
  • sha1() - Calcula el 'hash' sha1 de un string
  • hash() - Genera un valor cifrado con base a un string
  • crypt() - Hash de cadenas de un sólo sentido
  • password_hash() - Crea un hash de contraseña

add a note add a note

User Contributed Notes 13 notes

radon8472 at radon-software dot net
2 years ago
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.

= base64_decode($_SERVER['HTTP_CONTENT_MD5']);
$post_data = file_get_contents("php://input");

raw2hex($rawMd5) == md5($post_data)) // Post-Data is okay
else                                    // Post-Data is currupted
Some ONE
10 months ago
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
for($i=0;$i<10000000;++$i) md5("$i");

while this one takes 2.77 seconds
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.
Shane Allen
15 years ago
From the documentation on Digest::MD5:
This function will concatenate all arguments, calculate the MD5 digest of this "message", and return it in binary form.

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: " . $myrow['password'];
>php original hash from text: 0aed5d740d7fab4201e885019a36eace
>hash from perl: c18c9c57cb3658a50de06491a70b75cd
sebastian dot haller at freesurf dot ch
11 years ago
It has been found, that hash('md5', 'string'); is faster than md5($string):
5 months ago
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.
terry _at_ scribendi_com
13 years ago
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.
dionyziz at deviantart dot com
10 years ago
Sometimes it's useful to get the actual, binary, md5 digest.
You can use this function for it:


function md5bin( $target ) {
$md5 = md5( $target );
$ret = '';

    for (
$i = 0; $i < 32; $i += 2 ) {
$ret .= chr( hexdec( $md5{ $i + 1 } ) + hexdec( $md5{ $i } ) * 16 );


8 years ago
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.
admin at gadelkareem dot com
10 years ago
MySQL MD() will not give you the same hash if character set is different.
ex :
#suppose table_name CHARSET=UTF8
#$md5 = md5('Städte'); # will give you a different hash than MySQL MD5()
#instead use
$md5 = md5(utf8_encode('Städte'));
$r = mysql_query("SELECT *, MD5(`word`) FROM `table_name` WHERE MD5(`word`) LIKE '{$md5}'");
$row= mysql_fetch_assoc($r) )

John S.
13 years ago
If you want to replicate CPAN Digest::MD5's function md5_base64 in PHP, use this code:


function md5_base64 ( $data )

programings at abv dot bg
4 years ago
This recursive function allow you to hash something in depth using md5().

function checksum($what, $depth = 1) {
if (!
md5(checksum($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:

for ($i = 1; $i <= 10; $i++) {
"$i. ".checksum("test", $i)."<br />";

It can be used for security purposes.
marzetti dot marco at NOSPAM dot gmail dot com
12 years ago
The complement of raw2hex


function hex2raw( $str ){
$chunks = str_split($str, 2);
$i = 0; $i < sizeof($chunks); $i++ ) {
$op .= chr( hexdec( $chunks[$i] ) );

7 years ago
This is not encryption..... it's only a sort of DIGEST
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