infinity-calculator

<?php

declare(strict_types=1);

class Calculator
{
    private $result;
    
    public function __construct(int $result = 0) 
    {
        $this->result = $result;
    }
    
    public function __invoke(int $number): self
    {
        $this->result += $number;
        
        return $this;
    }
    
    public function __toString(): string
    {
        return (string) $this->result;
    }
}


$calculator = new Calculator();

echo $calculator; // 0
echo $calculator(2)(3)(15); // 20
echo $calculator(2)(5)(5); // 32