# hash_pbkdf2

(PHP 5 >= 5.5.0, PHP 7)

hash_pbkdf2 — Generate a PBKDF2 key derivation of a supplied password

### Description

hash_pbkdf2 ( string `$algo` , string `$password` , string `$salt` , int `$iterations` [, int `$length` = 0 [, bool `$raw_output` = `FALSE` ]] ) : string

### Parameters

`algo`

  Name of selected hashing algorithm (i.e. md5, sha256, haval160,4, etc..) See hash_algos() for a list of supported algorithms.

`password`

  The password to use for the derivation.

`salt`

  The salt to use for the derivation. This value should be generated randomly.

`iterations`

  The number of internal iterations to perform for the derivation.

`length`

  The length of the output string. If `raw_output` is `TRUE` this corresponds to the byte-length of the derived key, if `raw_output` is `FALSE` this corresponds to twice the byte-length of the derived key (as every byte of the key is returned as two hexits).

  If 0 is passed, the entire output of the supplied algorithm is used.

`raw_output`

  When set to `TRUE`, outputs raw binary data. `FALSE` outputs lowercase hexits.

### Return Values

Returns a string containing the derived key as lowercase hexits unless `raw_output` is set to `TRUE` in which case the raw binary representation of the derived key is returned.

### Errors/Exceptions

An `E_WARNING` will be raised if the algorithm is unknown, the `iterations` parameter is less than or equal to 0, the `length` is less than 0 or the `salt` is too long (greater than `INT_MAX` - 4).

### Changelog

Version | Description
--- | ---
7.2.0 | Usage of non-cryptographic hash functions (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat) was disabled.

### Examples

Example #1 hash_pbkdf2() example, basic usage

`<?php
$password = "password";
$iterations = 1000;
// Generate a random IV using openssl_random_pseudo_bytes()
// random_bytes() or another suitable source of randomness
$salt = openssl_random_pseudo_bytes(16);
$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
echo $hash;
?>`

The above example will output something similar to:

    120fb6cffcf8b32c43e7

### Notes

Caution

The PBKDF2 method can be used for hashing passwords for storage. However, it should be noted that password_hash() or crypt() with `CRYPT_BLOWFISH` are better suited for password storage.

### See Also

- crypt() - One-way string hashing
- password_hash() - Creates a password hash
- hash() - Generate a hash value (message digest)
- hash_algos() - Return a list of registered hashing algorithms
- hash_init() - Initialize an incremental hashing context
- hash_hmac() - Generate a keyed hash value using the HMAC method
- hash_hmac_file() - Generate a keyed hash value using the HMAC method and the contents of a given file
- openssl_pbkdf2() - Generates a PKCS5 v2 PBKDF2 string