Compare character change count between string

compare_string_change.php

<?php 

$str_one = "PASS12345";
$str_two = "PASSWOD45";

$str_one_arr = str_split($str_one);
$new_arr = str_split($str_two);

$arr_intersect = array_intersect($new_arr, $str_one_arr);
$arr_changes = array_diff($new_arr, $arr_intersect);

$change = abs(sizeof($str_one_arr) - sizeof($arr_intersect)) + sizeof($arr_changes);

?>