无法将类型为_PHP_complete_类的对象用作数组（会话相关？）

我有3个独立的文件，

item.php

，

proposal.php

和

output.php

-这应该是一个类似购物车的应用程序，其目的是让用户选择一个项目，并将项目放入

proposal

类中。。。但是，我遇到了以下错误：

致命错误：未捕获错误：无法在C:\xampp\htdocs\proposal.PHP中使用类型为uu PHP\u complete\u类的对象作为数组。PHP:12堆栈跟踪：#0 C:\xampp\htdocs\output.PHP（9）：proposal->addItem（object（Item））#1{main}在C:\xampp\htdocs\proposal.PHP的第12行抛出

我搜索了SO&Google，尝试了各种方法，包括将

session\u start（）

放在

item.php

和

proposal.php

的includes之前，但这并没有解决问题，错误只是变为：

无法将建议类型的对象用作数组

有什么想法吗？运行PHP7.0.9

item.php

<?php

    class Item {
        protected $id;
        protected $name;
        protected $manufacturer;
        protected $model;
        protected $qty;
        protected $serial;

        public function __construct($id,$name,$manufacturer,$model,$qty,$serial) {
            $this->id = $id;
            $this->name = $name;
            $this->manufacturer = $manufacturer;
            $this->model = $model;
            $this->qty = $qty;
            $this->serial = $serial;
        }

        public function getId() {
            return $this->id;
        }

        public function getName() {
            return $this->name;
        }

        public function getManufacturer() {
            return $this->manufacturer;
        }

        public function getModel() {
            return $this->model;
        }

        public function getQty() {
            return $this->qty;
        }

        public function getSerial() {
            return $this->serial;
        }                                
    }

    class Proposal {
        protected $items = array();

        public function __construct() {
            $this->items = isset($_SESSION['proposal']) ? $_SESSION['proposal'] : array();
        }

        public function addItem(Item $item) {
            $id = $item->getId();
            // the following line is line 12 of proposal.php
            if(isset($this->items[$id])) {
                $this->items[$id]['qty'] = $this->items[$id]['qty'] + $item->getQty();
            }
            else {
                $this->items[$id] = $item;
            }
        }
    }

    session_start();
    include('item.php');
    include('proposal.php');

    $item = new Item($_GET['id'],$_GET['name'],$_GET['manufacturer'],$_GET['model'],$_GET['qty'],$_GET['serial']);
    $proposal = new Proposal();

    $proposal->addItem($item);

    $_SESSION['proposal'] = $proposal;

    // view output in array/object format if session variable set
    if(isset($_SESSION['proposal'])) { print '<pre>' . print_r($_SESSION['proposal'],1) . '</pre>'; }

output.php

<?php

    class Item {
        protected $id;
        protected $name;
        protected $manufacturer;
        protected $model;
        protected $qty;
        protected $serial;

        public function __construct($id,$name,$manufacturer,$model,$qty,$serial) {
            $this->id = $id;
            $this->name = $name;
            $this->manufacturer = $manufacturer;
            $this->model = $model;
            $this->qty = $qty;
            $this->serial = $serial;
        }

        public function getId() {
            return $this->id;
        }

        public function getName() {
            return $this->name;
        }

        public function getManufacturer() {
            return $this->manufacturer;
        }

        public function getModel() {
            return $this->model;
        }

        public function getQty() {
            return $this->qty;
        }

        public function getSerial() {
            return $this->serial;
        }                                
    }

    class Proposal {
        protected $items = array();

        public function __construct() {
            $this->items = isset($_SESSION['proposal']) ? $_SESSION['proposal'] : array();
        }

        public function addItem(Item $item) {
            $id = $item->getId();
            // the following line is line 12 of proposal.php
            if(isset($this->items[$id])) {
                $this->items[$id]['qty'] = $this->items[$id]['qty'] + $item->getQty();
            }
            else {
                $this->items[$id] = $item;
            }
        }
    }

    session_start();
    include('item.php');
    include('proposal.php');

    $item = new Item($_GET['id'],$_GET['name'],$_GET['manufacturer'],$_GET['model'],$_GET['qty'],$_GET['serial']);
    $proposal = new Proposal();

    $proposal->addItem($item);

    $_SESSION['proposal'] = $proposal;

    // view output in array/object format if session variable set
    if(isset($_SESSION['proposal'])) { print '<pre>' . print_r($_SESSION['proposal'],1) . '</pre>'; }

在声明类之前，会话已初始化

这导致了uu PHP_不完整的u类

“无法将建议类型的对象用作数组”的问题：

如果会话包含键

建议

，则将其用作存储变量，但在

output.php中将其初始化为
建议
的实例：

class Proposal {
    protected function __construct() {}

    public static function getInstance()
    {
        if (!isset($_SESSION['proposal'])) {
            $_SESSION['proposal'] = new Proposal;
        }

        return $_SESSION['proposal'];
    }
}


避免这种情况的一种方法是创建一个单独的提案会话：

这确实解决了我在上述两个错误中遇到的问题，但是生成了另一个错误“无法将Item类型的对象用作数组”。我发现这个新错误是由以下行引起的：
$this->items[$id]['qty']=$this->items[$id]['qty']+$item->getQty（）我通过将代码更改为
$this->items[$id]->qty=$this->items[$id]->qty+$item->getQty（）来更正此问题存在的问题是，我试图以数组的形式不正确地访问item对象。谢谢你的回答！
class Proposal {
    protected function __construct() {}

    public static function getInstance()
    {
        if (!isset($_SESSION['proposal'])) {
            $_SESSION['proposal'] = new Proposal;
        }

        return $_SESSION['proposal'];
    }
}