class Mianji
{
private $chang;
private $kuan;
function __construct($c,$k)
{
$this->chang=$c;
$this->kuan=$k;
}
function MJ()
{
return $this->chang*$this->kuan;
}
}
$da=new Mianji(10,10);
$xo=new Mianji(6,5);
echo $yy=$da->MJ()-$xo->MJ();