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Created July 10, 2013 21:45
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[ Posted by Fiddler ] This function calculates how strong a password choice is. A strong password has a value that is as close to possible to 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"));
?>
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