Latihan : Membuat Kalkulator Sederhana Dengan OOP

<?php
	/*
	* Kalkulator Sederhana Dengan PHP OOP
	*/

class Kalkulator{
	// Property
  	private $x;
  	private $y;

	function __construct($bil1,$bil2){
		$this->x = $bil1;
		$this->y = $bil2;
	}

	public function tambah(){
		$hasil = $this->x + $this->y;
    	return $hasil;
	}

	public function kurang(){
		$hasil = $this->x - $this->y;
    	return $hasil;
	}

	public function bagi(){
		$hasil = $this->x / $this->y;
    	return $hasil;
	}

	public function kali(){
		$hasil = $this->x * $this->y;
    	return $hasil;
	}
}

echo "<form action='' method='post'>
Bilangan 1 : <input type='text' name='bil1' />
<select name='operator'>
	<option value='tambah'>+</option>
	<option value='kurang'>-</option>
	<option value='bagi'>:</option>
	<option value='kali'>x</option>
</select>
Bilangan 2 : <input type'text' name='bil2' />
<input type='submit' name='hitung' value='Hitung'/>
</form>";

if(isset($_POST['hitung'])){
	$bil1 = $_POST['bil1'];
	$bil2 = $_POST['bil2'];
	$operator = $_POST['operator'];
	$kalkulator = new Kalkulator($bil1,$bil2);
	switch($operator) {
		case 'tambah':
			echo "Hasil dari ".$bil1." + ".$bil2." = ".$kalkulator->tambah();
			break;
		case 'kurang':
			echo "Hasil dari ".$bil1." - ".$bil2." = ".$kalkulator->kurang();
			break;
		case 'kali':
			echo "Hasil dari ".$bil1." x ".$bil2." = ".$kalkulator->kali();
			break;
		case 'bagi':
			echo "Hasil dari ".$bil1." : ".$bil2." = ".$kalkulator->bagi();
			break;
		default:
			break;
	}
}