(PHP 5 >= 5.5.0)
openssl_pbkdf2 — Generates a PKCS5 v2 PBKDF2 string, defaults to SHA-1
$password
   , string $salt
   , int $key_length
   , int $iterations
   [, string $digest_algorithm
  ] )
This function is currently not documented; only its argument list is available.
password
salt
key_length
iterations
digest_algorithm
   Returns string or FALSE on failure.