PPH21Calculator.php

<?php

class PPH21Calculator
{
    private function firstRule(float $pkp): float
    {
        if (0 < $pkp && 50000000 >= $pkp) {//0 - 50jt
            return $pkp * 0.05;
        }

        return 0;
    }

    private function secondRule(float $pkp): float
    {
        if (50000000 < $pkp && 250000000 >= $pkp) {//50jt - 250jt
            $pkp -= 50000000;

            $prev = $this->firstRule(50000000);

            return ($pkp * 0.15) + $prev;
        }

        return 0;
    }

    private function thirdRule(float $pkp): float
    {
        if (250000000 < $pkp && 500000000 >= $pkp) {//250jt - 500jt
            $pkp -= 250000000;

            $prev = $this->secondRule(250000000);

            return ($pkp * 0.25) + $prev;
        }

        return 0;
    }

    private function fourthRule(float $pkp): float
    {
        if (500000000 < $pkp && 10000000000000 >= $pkp) {//> 500jt
            $pkp -= 500000000;

            $prev = $this->thirdRule(500000000);

            return ($pkp * 0.3) + $prev;
        }

        return 0;
    }

    public function calculate(float $pkp): float
    {
        return $this->firstRule($pkp) ?: $this->secondRule($pkp) ?: $this->thirdRule($pkp) ?: $this->fourthRule($pkp);
    }
}

$pph21 = new PPH21Calculator();

//1250000
echo $pph21->calculate(25000000);
echo PHP_EOL;
//1500000
echo $pph21->calculate(30000000);
echo PHP_EOL;
//2250000
echo $pph21->calculate(45000000);
echo PHP_EOL;
//2500000
echo $pph21->calculate(50000000);
echo PHP_EOL;
//4000000
echo $pph21->calculate(60000000);
echo PHP_EOL;
//6250000
echo $pph21->calculate(75000000);
echo PHP_EOL;
//32500000
echo $pph21->calculate(250000000);
echo PHP_EOL;
//45000000
echo $pph21->calculate(300000000);
echo PHP_EOL;
//82500000
echo $pph21->calculate(450000000);
echo PHP_EOL;
//170000000
echo $pph21->calculate(750000000);
echo PHP_EOL;