Get array length in a PHP class

Question

I'm new to object oriented programming in PHP. I made a simple order class with an array property. The method orderLength is not working. I'm getting an error:

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();

Answer 1

您可以尝试使用以下内容代替$this->count(order)

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

Answer 2

Just return the count of $order:

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

Answer 3

Count是一个方法，而不是类属性，试试这个：

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

Answer 4

Simply you miske that line

$this -> count(order);

Your class has no member functions with the name count , so remove that:

this ->

Answer 5

You have not defined a method count for your class. The way you have done it, it looks like you are calling the count method of your class, giving order as an argument.

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

Answer 6

Assign the value to the variable $order and then write the code for getting the count:

$order = $order -> setOrder(array('Book1', 'Book2', 'Book3', 'Book4'));
echo "The order length is: ".$order->orderLength();