php計算密碼強度

下面的php代碼用于測試給定密碼的強度，最高強度為100

<?php
/**



@param String $string
@return float

Returns a float between 0 and 100. The closer the number is to 100 the
the stronger password is; further from 100 the weaker the password is.
*/
function password_strength($string){
 $h    = 0;
 $size = strlen($string);
 foreach(count_chars($string, 1) as $v){
 $p = $v / $size;
 $h -= $p * log($p) / log(2);

 }
 $strength = ($h / 4) * 100;
 if($strength > 100){
 $strength = 100;

 }
 return $strength;
}

var_dump(password_strength("Correct Horse Battery Staple"));
echo "<br>";
var_dump(password_strength("Super Monkey Ball"));
echo "<br>";
var_dump(password_strength("Tr0ub4dor&3"));
echo "<br>";
var_dump(password_strength("abc123"));
echo "<br>";
var_dump(password_strength("sweet"));</pre>