This package provides an interface to the cracklib (libcrack) libraries that
come standard on most Unix-like distributions. This allows you to check
passwords against dictionaries of words to ensure some minimal level of
password security.

From the cracklib README
CrackLib makes literally hundreds of tests to determine whether you've
chosen a bad password.

* It tries to generate words from your username and gecos entry to tries
to match them against what you've chosen.

* It checks for simplistic patterns.

* It then tries to reverse-engineer your password into a dictionary
word, and searches for it in your dictionary.

- after all that, it's PROBABLY a safe(-ish) password. 8-)

WWW: http://pecl.php.net/package/crack