[PHP] pobierz, plaintext 
echo $a = 'stackoverflow';
echo '<br>';
echo $b = '$2a$10$bf57caf7e1fa23e4b975ab';
echo '<br>CRYPT:<br>';
echo crypt($a, $b);
[PHP] pobierz, plaintext 

stackoverflow
$2a$10$bf57caf7e1fa23e4b975ab
CRYPT:
$2.LaeiP21fsQ

stackoverflow
$2a$10$bf57caf7e1fa23e4b975ab
CRYPT:
$2a$10$bf57caf7e1fa23e4b975aOhXjTtYrqOYLfHsxdOxGRhF03.LtKewW

Jeśli nie, to po prostu zrezugnuj z funkcji crypt i skorzystaj z normalnego hashowania z solą.

Why are common hashing functions such as md5() and sha1() unsuitable for passwords?
Hashing algorithms such as MD5, SHA1 and SHA256 are designed to be very fast and efficient. With modern techniques and computer equipment, it has become trivial to "brute force" the output of these algorithms, in order to determine the original input.
Because of how quickly a modern computer can "reverse" these hashing algorithms, many security professionals strongly suggest against their use for password hashing.

"$2C9b17FGUTd." is not a valid Blowfish hash. You got this output on earlier versions of PHP where CRYPT_BLOWFISH was not supported, or perhaps a buggy version was being used. PHP 5.3.8 is returning the correct hash.

I dlatego szukam innego rozwiązania aby nie stracić tych danych albo nie wymuszać zmiany haseł.

To zmień je w locie zaraz przy zalogowaniu.

Ale wypadałoby najpierw jakoś sprawdzić, czy dane logowania się zgadzają