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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.


md5 ( string $str , bool $raw_output = false ) : string

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() - Generar un valor hash (resumen de mensaje)
  • crypt() - Hash de cadenas de un sólo sentido
  • password_hash() - Crea un hash de contraseña

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User Contributed Notes 9 notes

Ray.Paseur sometimes uses Gmail
2 years ago
md5('240610708') == md5('QNKCDZO')

This comparison is true because both md5() hashes start '0e' so PHP type juggling understands these strings to be scientific notation.  By definition, zero raised to any power is zero.
11 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.
yiminrong at yahoo dot ca
1 month ago
Regarding Ray Paseur's comment, the strings hash to:


The odds of getting a hash exactly matching the format /^0+e[0-9]+$/ are not high but are also not negligible.

It should be added as a general warning for all hash functions to always use the triple equals === for comparison.

Actually, the warning should be in the operators section when comparing string values! There are lots of warnings about string comparisons, but nothing specific about the format /^0+e[0-9]+$/.
radon8472 at radon-software dot net
4 years ago
function raw2hex($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
Shane Allen
17 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
3 years 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
15 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.
Steve M
1 year ago
I've found multiple sites suggesting the code:


Until recently, I hadn't noticed any issues with this locally... but then I tried to hash a 700MB file, with a 2048MB memory limit and kept getting out of memory errors...

There appears to be a limit to how long a string the md5() function can handle, and the alternative function is likely more memory efficient anyway. I would highly recommend to all who need file hashing (for detecting duplicates, not security digests) use the md5_file() function and NOT the regular string md5() function!


Note, to those interested, as this was for a local application not a server, I was more concerned with results than memory efficiency. In a live environment, you would never want to read an entire file into memory at once when avoidable. (at the time of coding, I did not know of the alternative function)
dionyziz at deviantart dot com
13 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 );


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