我正在尝试使用此php函数执行一个散列密码的功能：http://be.php.net/manual/en/function.hash-pbkdf2.php。
这是代码：
$hash_algo = "sha256";
$password = "password";
$salt = "salt";
$iterations = 1;
$length = 1;
$raw_output = false;
$hash = hash_pbkdf2($hash_algo, $password, $salt, $iterations ,$length ,$raw_output);
echo $hash;
我收到此错误：致命错误：调用未定义的函数 hash_pbkdf2（）。
函数怎么可能未定义???
PS：我的变量的所有值都是为了测试函数而设置的。显然，盐不会是"盐"等。
编辑：截至PHP 5.5.0，此函数现已捆绑到核心库中。
这个函数在核心 PHP 中（无论如何）不可用。它是不久前提出的，到目前为止，您只能将其作为补丁获得。
您可以改用crypt或hash。 crypt实际上hash_pbkdf2文档中建议
谨慎
PBKDF2 方法可用于对存储密码进行哈希处理（它已获得 NIST 批准用于该用途）。但是，应该注意的是，CRYPT_BLOWFISH更适合密码存储，应改为通过crypt().
如果您自己包含该函数，则可以使用PBKDF2。只需将此网站上的代码粘贴到您的应用程序中，就再简单不过了。 该代码是公共领域（如该站点所述）。
以下是完整的代码：
<?php
/*
* Password hashing with PBKDF2.
* Author: havoc AT defuse.ca
* www: https://defuse.ca/php-pbkdf2.htm
*/
// These constants may be changed without breaking existing hashes.
define("PBKDF2_HASH_ALGORITHM", "sha256");
define("PBKDF2_ITERATIONS", 1000);
define("PBKDF2_SALT_BYTES", 24);
define("PBKDF2_HASH_BYTES", 24);
define("HASH_SECTIONS", 4);
define("HASH_ALGORITHM_INDEX", 0);
define("HASH_ITERATION_INDEX", 1);
define("HASH_SALT_INDEX", 2);
define("HASH_PBKDF2_INDEX", 3);
function create_hash($password)
{
// format: algorithm:iterations:salt:hash
$salt = base64_encode(mcrypt_create_iv(PBKDF2_SALT_BYTES, MCRYPT_DEV_URANDOM));
return PBKDF2_HASH_ALGORITHM . ":" . PBKDF2_ITERATIONS . ":" . $salt . ":" .
base64_encode(pbkdf2(
PBKDF2_HASH_ALGORITHM,
$password,
$salt,
PBKDF2_ITERATIONS,
PBKDF2_HASH_BYTES,
true
));
}
function validate_password($password, $good_hash)
{
$params = explode(":", $good_hash);
if(count($params) < HASH_SECTIONS)
return false;
$pbkdf2 = base64_decode($params[HASH_PBKDF2_INDEX]);
return slow_equals(
$pbkdf2,
pbkdf2(
$params[HASH_ALGORITHM_INDEX],
$password,
$params[HASH_SALT_INDEX],
(int)$params[HASH_ITERATION_INDEX],
strlen($pbkdf2),
true
)
);
}
// Compares two strings $a and $b in length-constant time.
function slow_equals($a, $b)
{
$diff = strlen($a) ^ strlen($b);
for($i = 0; $i < strlen($a) && $i < strlen($b); $i++)
{
$diff |= ord($a[$i]) ^ ord($b[$i]);
}
return $diff === 0;
}
/*
* PBKDF2 key derivation function as defined by RSA's PKCS #5: https://www.ietf.org/rfc/rfc2898.txt
* $algorithm - The hash algorithm to use. Recommended: SHA256
* $password - The password.
* $salt - A salt that is unique to the password.
* $count - Iteration count. Higher is better, but slower. Recommended: At least 1000.
* $key_length - The length of the derived key in bytes.
* $raw_output - If true, the key is returned in raw binary format. Hex encoded otherwise.
* Returns: A $key_length-byte key derived from the password and salt.
*
* Test vectors can be found here: https://www.ietf.org/rfc/rfc6070.txt
*
* This implementation of PBKDF2 was originally created by https://defuse.ca
* With improvements by http://www.variations-of-shadow.com
*/
function pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false)
{
$algorithm = strtolower($algorithm);
if(!in_array($algorithm, hash_algos(), true))
die('PBKDF2 ERROR: Invalid hash algorithm.');
if($count <= 0 || $key_length <= 0)
die('PBKDF2 ERROR: Invalid parameters.');
$hash_length = strlen(hash($algorithm, "", true));
$block_count = ceil($key_length / $hash_length);
$output = "";
for($i = 1; $i <= $block_count; $i++) {
// $i encoded as 4 bytes, big endian.
$last = $salt . pack("N", $i);
// first iteration
$last = $xorsum = hash_hmac($algorithm, $last, $password, true);
// perform the other $count - 1 iterations
for ($j = 1; $j < $count; $j++) {
$xorsum ^= ($last = hash_hmac($algorithm, $last, $password, true));
}
$output .= $xorsum;
}
if($raw_output)
return substr($output, 0, $key_length);
else
return bin2hex(substr($output, 0, $key_length));
}
?>
如果您需要了解有关哈希，盐，迭代和所有其他内容的任何信息，该网站有所有正确的答案。
你可以在手册中找到这个。
（没有可用的版本信息，可能只有SVN）
这意味着此功能不可用。
更新
现在hash_pbkdf2可用于 （PHP 5>= 5.5.0， PHP 7）。
文档 ： http://be.php.net/manual/en/function.hash-pbkdf2.php