<?php

$a = [1 => 1, 2 => 2];
$b = [...$a, 3 => 3, 1 => 4];

dump($b);

^ array:3 [

  0 => 1

  1 => 4

  3 => 3

]

• Sort your data for each country individually
• PHP XSLTProcessor
• A calendar written with IntlCalendar class

PHP 8.2, Laminas MVC 3.2, Symfony 5.2, Laravel 8.28, PHPUnit 9.5, Doctrine ORM 2.8