fisher-yates-shuffle.php

<?php
/**
 *  It's an algorithm for generating a random permutation of a finit sequence - in plain terms, the algorithm shuffles the sequence.
 *
 *  Reference: https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
 */


function MyShuffle(&$arr) {

         for($i = 0; $i < sizeof($arr); ++$i) {
             $r = rand(0, $i);
             $tmp = $arr[$i];
             $arr[$i] = $arr[$r];
             $arr[$r] = $tmp;  
         }
};

echo"<h2>Hello Fisher-Yates Shuffle Algorithm</h2>";

$arr = array(0,1,2,3,4,5,6,7,8,9);

echo"<pre>";
print_r($arr);
echo"</pre>";

MyShuffle($arr);

echo"<pre>";
print_r($arr);
echo"</pre>";
      
?>

Hi,

An Excelent contribution, but you can better your algomithm, whith the next suggerens:

1º. Not use var with reference, the function has must return your values.(In new versions of php not work the reference)
2º. Not use indexOf(), use count() is more faster and readable for other developers.
3º. The Fisher-Yates Shuffle walk the array in reverse order.

function myShuffle($arr) {
for($i = count($arr) - 1; $i > 0; $i--) {
$r = rand(0, $i);
$tmp = $arr[$i];
$arr[$i] = $arr[$r];
$arr[$r] = $tmp;
}

 return $arr;

}

$arr = [1, 2, 3, 4];

print_r($arr);
print_r(myShuffle($arr));

I hope help you.

Best regards.