当一个类的构造函数被定义为private时如何创建该类的实例

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class Goods{

private $Name;

private $Price;

private $Color;

private $type;

private $goods;

private function __construct($Name,$Price,$Color,$type){

$this->Name=$Name;

$this->Price=$Price;

$this->Color=$Color;

$this->type=$type;

}

function getIstance(){

if($goods==null)

$goods=new Goods("面包",3.5,"橙黄","食品");

return $goods;

}

function __destruct(){

echo "清除价格",$this->Price;

}

}

Goods::getIstance();

?>