Home » PHP » PHP_Compat » Bug #5078

[2005-08-12 16:16 UTC] mina86 at tlen dot pl

Description:
------------
The current implementation of str_shuffle() is (not to use dirt words) wrong. The bug is since the revision 1.2 of str_shuffle.php file.

Test script:
---------------
<?php
function my_str_shuffle($str) {
$newstr = ''; $strlen = strlen($str); $str = (string) $str;
list($usec, $sec) = explode(' ', microtime());
$seed = (float) $sec + ((float) $usec * 100000);
mt_srand($seed);
for ($i = 0; $strlen > $i; $i++) $newstr .= $str[mt_rand(0, $strlen - 1)];
return $newstr;
}
for ($i = 0; $i<10; ++$i) echo(my_str_shuffle('123') . ' ');
?>

--- correct version --

function str_shuffle($str) {
if (($l=strlen($str=(string)$str))<2) return $str;
list($us, $s) = explode(' ', microtime());
mt_srand((int)$s + (int)((float)$us * 100000));
for ($s=''; $l!==0; $str{$p}=$str{$l}) $s.=$str{$p=mt_rand(0, --$l)};
return $s;
}

Expected result:
----------------
Ten *permutations* of string '123'.

Actual result:
--------------
Definitly not permutations but something like: 312 221 133 331 113 333 212 331 232 111