Classes and Objects in PHP OOP

<?php 

class Product {
    public $id;
    public $name;
    public $price;
    public $quantity;
}

$product = new Product();
$product->id = 'p01';
$product->name = 'name 1';
$product->price = 4.5;
$product->quantity = 2;

echo 'Product Info';
echo '<br>id: '.$product->id;
echo '<br>name: '.$product->name;
echo '<br>price: '.$product->price;
echo '<br>quantity: '.$product->quantity;
echo '<br>total: '.($product->price * $product->quantity);

?>

Output

Product Info
id: p01
name: name 1
price: 4.5
quantity: 2
total: 9