<?php

$myArray = [
 0 => [
  'id' => 1,
  'title' => 'title1'
 ],
 1 => [
  'id' => 2,
  'title' => 'title2'
 ],
 2 => [
  'id' => 3,
  'title' => 'title3'
 ],
 3 => [
  'id' => 4,
  'title' => 'title4'
 ]
];


foreach ($myArray as $key => $item)
{
 $myArray[$key]['funcResult'] = $item['id'];
}
unset($key);


print_r($myArray);