Password Validator for PHP

Password Validator validates password_hash generated passwords, rehashes passwords as necessary, and will upgrade legacy passwords.

Password Validator is available for all versions of PHP >= 5.3.7.


The only officially supported method of installation is via Composer.

Create a composer.json file in the root of your project (always check Packagist for the most recent version):

    "require": {
        "jeremykendall/password-validator": "*"

And then run: composer install

Add the autoloader to your project:


require_once '../vendor/autoload.php'

You're now ready to begin using the Password Validator.


Password Validation

If you're already using password_hash generated passwords in your application, you need do nothing more than add the validator in your authentication script. The validator uses password_verify to test the validity of the provided password hash.

use JeremyKendall\Password\PasswordValidator;

$validator = new PasswordValidator();
$result = $validator->isValid($_POST['password'], $hashedPassword);

if ($result->isValid()) {
    // password is valid

If your application requires options other than the password_hash defaults, you can set both the salt and cost options with PasswordValidator::setOptions().

$options = array(
    'salt' => 'SettingYourOwnSaltIsNotTheBestIdea',
    'cost' => 11,

IMPORTANT: PasswordValidator uses a default cost of 10. If your existing hash implementation requires a different cost, make sure to specify it using PasswordValidator::setOptions(). If you do not do so, all of your passwords will be rehashed using a cost of 10.


Each valid password is tested using password_needs_rehash. If a rehash is necessary, the valid password is hashed using password_hash with the provided options. The result code Result::SUCCESS_PASSWORD_REHASHED will be returned from Result::getCode() and the new password hash is available via Result::getPassword().

if ($result->getCode() === Result::SUCCESS_PASSWORD_REHASHED) {
    $rehashedPassword = $result->getPassword();
    // Persist rehashed password

IMPORTANT: If the password has been rehashed, it's critical that you persist the updated password hash. Otherwise, what's the point, right?

Upgrading Legacy Passwords

You can use the PasswordValidator whether or not you're currently using password_hash generated passwords. The validator will transparently upgrade your current legacy hashes to the new password_hash generated hashes as each user logs in. All you need to do is provide a validator callback for your password hash and then decorate the validator with the UpgradeDecorator.

use JeremyKendall\Password\Decorator\UpgradeDecorator;

// Example callback to validate a sha512 hashed password
$callback = function ($password, $passwordHash, $salt) {
    if (hash('sha512', $password . $salt) === $passwordHash) {
        return true;

    return false;

$validator = new UpgradeDecorator(new PasswordValidator(), $callback);
$result = $validator->isValid('password', 'password-hash', 'legacy-salt');

The UpgradeDecorator will validate a user's current password using the provided callback. If the user's password is valid, it will be hashed with password_hash and returned in the Result object, as above.

All password validation attempts will eventually pass through the PasswordValidator. This allows a password that has already been upgraded to be properly validated, even when using the UpgradeDecorator.

Persisting Rehashed Passwords

Whenever a validation attempt returns Result::SUCCESS_PASSWORD_REHASHED, it's important to persist the updated password hash.

if ($result->getCode() === Result::SUCCESS_PASSWORD_REHASHED) {
    $rehashedPassword = $result->getPassword();
    // Persist rehashed password

While you can always perform the test and then update your user database manually, if you choose to use the Storage Decorator all rehashed passwords will be automatically persisted.

The Storage Decorator takes two constructor arguments: An instance of PasswordValidatorInterface and an instance of the JeremyKendall\Password\Storage\StorageInterface.


The StorageInterface includes a single method, updatePassword(). A class honoring the interface might look like this:


namespace Example;

use JeremyKendall\Password\Storage\StorageInterface;

class UserDao implements StorageInterface
    public function __construct(\PDO $db)
        $this->db = $db;

    public function updatePassword($identity, $password)
        $sql = 'UPDATE users SET password = :password WHERE username = :identity';
        $stmt = $this->db->prepare($sql);
        $stmt->execute(array('password' => $password, 'username' => $identity));

Storage Decorator

With your UserDao in hand, you're ready to decorate a PasswordValidatorInterface.

use Example\UserDao;
use JeremyKendall\Password\Decorator\StorageDecorator;

$storage = new UserDao($db);
$validator = new StorageDecorator(new PasswordValidator(), $storage);

// If validation results in a rehash, the new password hash will be persisted
$result = $validator->isValid('password', 'passwordHash', null, 'username');

IMPORTANT: You must pass the optional fourth argument ($identity) to isValid() when calling StorageDecorator::isValid(). If you do not do so, the StorageDecorator will throw an IdentityMissingException.

Validation Results

Each validation attempt returns a JeremyKendall\Password\Result object. The object provides some introspection into the status of the validation process.

  • Result::isValid() will return true if the attempt was successful
  • Result::getCode() will return one of three possible int codes:
    • Result::SUCCESS if the validation attempt was successful
    • Result::SUCCESS_PASSWORD_REHASHED if the attempt was successful and the password was rehashed
    • Result::FAILURE_PASSWORD_INVALID if the attempt was unsuccessful
  • Result::getPassword() will return the rehashed password, but only if the password was rehashed

Database Schema Changes

As mentioned above, because this library uses the PASSWORD_DEFAULT algorithm, it's important your password field be VARCHAR(255) to account for future updates to the default password hashing algorithm.

cost-check Helper Script

The default cost used by password_hash is 10. This may or may not be appropriate for your production hardware, and it's entirely likely you can use a higher cost than the default. cost-check is based on the finding a good cost example in the PHP documentation. Simply run ./vendor/bin/cost-check from the command line and an appropriate cost will be returned.

NOTE: The default time target is 0.2 seconds. You may choose a higher or lower target by passing a float argument to cost-check, like so:

$ ./vendor/bin/cost-check 0.4
Appropriate 'PASSWORD_DEFAULT' Cost Found:  13