<?php
function customArray(array $array):array {
  $ilk_iki_eleman = [
  $array[0],
  $array[1],
];
  $ilk_iki_cikar = array_slice($array, 2);
shuffle($ilk_iki_cikar);
return array_merge($ilk_iki_eleman, $ilk_iki_cikar);
}
$test_array = [
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
];
$final_array = customArray($test_array);
print_r($final_array);