public function getPrice() { return $this->price; } public function adjustPrice($price) { if (false == $this->checkPrice($price)) { throw new Exception('価格の設定値が不正です'); } $this->price += $price; } private function checkPrice($count) { if (false == is_numeric($count)) { return false; } return true; } } try { $prd = new Product(100); echo $prd->getPrice() . '円です。<br>'; $prd->adjustPrice(200); echo $prd->getPrice() . '円です。<br>'; $prd2 = new Product('あああ'); echo $prd2->getPrice() . '円です<br>'; $prd2->adjustPrice('いいい'); echo $prd2->getPrice() . '円です<br>'; } catch (Exception $e) { echo $e->getMessage(); }