- crypt: documentation ( source)
- str_repeat: documentation ( source)
<?php
$setting = '$2a$04$';
$salt = '1234567890123456789012'; // SAME SALT FOR ALL PASSWORDS, OMG, DON'T
$passwd1 = str_repeat('A', 256);
$passwd2 = str_repeat('A', 513);
$hash1 = crypt($passwd1, $setting . $salt);
$hash2 = crypt($passwd2, $setting . $salt);
echo ($hash1 === $hash2 ? 'same' : 'unique');