php计算密码强度

下面的php代码用于测试给定密码的强度，最高强度为100

1. /**
2. *
3. * @param String $string
4. * @return float
5. *
6. * Returns a float between 0 and 100. The closer the number is to 100 the
7. * the stronger password is; further from 100 the weaker the password is.
8. */
9. function password_strength($string){
10. $h = 0;
11. $size = strlen($string);
12. foreach(count_chars($string, 1) as $v){
13. $p = $v / $size;
14. $h -= $p * log($p) / log(2);
15. }
16. $strength = ($h / 4) * 100;
17. if($strength > 100){
18. $strength = 100;
19. }
20. return $strength;
21. }
23. var_dump(password_strength("Correct Horse Battery Staple"));
24. echo "
    ";
25. var_dump(password_strength("Super Monkey Ball"));
26. echo "
    ";
27. var_dump(password_strength("Tr0ub4dor&3"));
28. echo "
    ";
29. var_dump(password_strength("abc123"));
30. echo "
    ";
31. var_dump(password_strength("sweet"));