警告：在第 16 行从空值创建默认对象答案

【问题标题】：Warning: Creating default object from empty value in on line 16警告：在第 16 行从空值创建默认对象
【发布时间】：2018-04-22 22:20:14
【问题描述】：

我的 PHP 代码“警告：从空值创建默认对象”中出现错误，代码如下：

class carshop
{
    public $cars = array();
    public $car_brand,$car_name, $car_modal,$car_price;

    public function set_cars($car_brand,$car_name,$car_modal,$car_price)
    {

        $n_cars = count($this->cars);

错误行从这里开始：

        $this->cars[$n_cars]->car_brand = $car_brand;
        $this->cars[$n_cars]->car_name = $car_name;
        $this->cars[$n_cars]->car_modal = $car_modal;
        $this->cars[$n_cars]->car_price = $car_price;
    }



    public function print_cars()
    {
        echo "<b>Car Stock: </b> We Have " 
        .count($this->cars). " Cars Infromation ! </br></br>";
        for ($i=0; $i < count($this->cars) ; $i++) { 
            echo "<b><u>Car No: ".$i."</u></b> " 
            .$this->cars[$i]->car_brand. " ,"
             .$this->cars[$i]->car_name. " ,"
              .$this->cars[$i]->car_modal. " , \$"
               .$this->cars[$i]->car_price;
            echo "</br>";
        }
    }
}

对象从这里开始：

$shop = new carshop();
$shop->set_cars("Honda","Civic","2017",2400000);
$shop->set_cars("Honda","City","2012",1200000);
$shop->set_cars("Honda","Accord","2015",1100000);
$shop->print_cars();

【问题讨论】：

$this->cars 是 array 而不是 object。你应该这样做：$this->cars[$n_cars]['car_brand'] = $car_brand;

标签： php

【解决方案1】：

carshop 类的$cars 字段作为数组：

public $cars = array();

从代码中，我推测您打算将其作为一组汽车。发生错误是因为您正在这样做：

$this->cars[$n_cars]->car_brand = $car_brand;

但是$this->cars[$n_cars]的值是null。

也许您可以拆分班级 - 一个负责处理汽车商店的业务逻辑，另一个负责代表汽车。如：

class Car
{
    public $car_brand, $car_name, $car_modal, $car_price;
}

class CarShop
{
    public $cars = array();

    public function set_cars($car_brand,$car_name,$car_modal,$car_price)
    {
        $n_cars = count($this->cars);
        $this->cars[$n_cars] = new Car();  // <-- Create a new Car object and add it to the cars array
        $this->cars[$n_cars]->car_brand = $car_brand;
        $this->cars[$n_cars]->car_name = $car_name;
        $this->cars[$n_cars]->car_modal = $car_modal;
        $this->cars[$n_cars]->car_price = $car_price;
    }

    // ... Rest of your CarShop class here
}

【讨论】：