Cracklib
Установка и настройка
Cracklib
PHP Manual

# Введение

These functions allow you to use the CrackLib library to test the 'strength' of a password. The 'strength' of a password is tested by that checks length, use of upper and lower case and checked against the specified CrackLib dictionary. CrackLib will also give helpful diagnostic messages that will help 'strengthen' the password.

> Замечание: This extension has been moved to the » PECL repository and is no longer bundled with PHP as of PHP 5.0.0.

Cracklib
Установка и настройка
Cracklib
PHP Manual