获取php类中的数组长度

我是PHP中面向对象编程的新手.
我创建了一个带有数组属性的简单订单类.
方法orderLength不起作用.我得到一个错误.

Call to undefined method Order::count()

PHP：

<?PHP       
    class Order {
        private $order = array();

        public function setorder($wert) {
            foreach($wert as $value) {
                $this -> order[] = $value;
            }
        }

        public function orderLength() {
            $length = $this -> count(order);
            return $length;
        }

        public function returnorder() {
            $value = $this -> order;
            return $value;
        }
    }   

    $order = new Order;
    $order -> setorder(array('Book1','Book2','Book3','Book4'));

    foreach($order->returnorder() as $value) {
        echo $value."<br>";
    }

    echo "The order Length is: ".$order->orderLength();

解决方法

您可以尝试使用以下内容代替$this-> count(order)

$length = count($this->order);