<?php
// first:
// $ composer require php-coord/php-coord

require_once __DIR__ . '/vendor/autoload.php';

// EPSG 25833 is UTM 33 North, see https://epsg.io/25833
$UTMRef = new \PHPCoord\UTMRef(350531.8, 5689109.2, 0, 'N', 33);
$LatLng = $UTMRef->toLatLng();

echo (string) $UTMRef . "\n";
echo (string) $LatLng . "\n";
?>