class UnitCounter

{

    var $units;

    var $weightPerUnit;

   

    function add($n=1)

    {

        $this->units = $this->units + $n;

    }

   

    function totalWeight()

    {

        return $this->units * $this->weightPerUnit;

    }

   

    function __construct($unitWeight=1.0)

    {

        $this->weightPerUnit = $unitWeight;

        $this->units = 0;

    }

}

 

 

$bottles = new UnitCounter(1.5);

   

    if(isset($_POST['go']))

    {

        $bottles->add($_POST['bottles']);

    }

        print $bottles->totalWeight();

 

 

$bottles = new UnitCounter(1.2);

    $bottles->add(3);

    print $bottles->totalWeight() . "<br />";

    $bottles->add(4);

    print $bottles->totalWeight()