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(PHP 5 >= 5.5.0)

hash_pbkdf2Generate a PBKDF2 key derivation of a supplied password


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



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


The password to use for the derivation.


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


The number of internal iterations to perform for the derivation.


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.


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.


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).


Example #1 hash_pbkdf2() example, basic usage

$iterations 1000;

// Generate a random IV using mcrypt_create_iv(),
// openssl_random_pseudo_bytes() or another suitable source of randomness
$salt mcrypt_create_iv(16MCRYPT_DEV_URANDOM);

$hash hash_pbkdf2("sha256"$password$salt$iterations20);

The above example will output something similar to:




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

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