<?php use gries\NumberSystem\HexadecimalSystem; use gries\NumberSystem\Number; require_once __DIR__ . '/../vendor/autoload.php'; $number = new Number(15); // the default system is decimal $hexNumber = new Number('FF', new HexadecimalSystem()); echo $number->add($hexNumber)->value(); // 270 (15 + 255) echo $hexNumber->add($number)->value(); // 10E (F + FF)