PHP，你怎么穿着品如的衣服？

### 运行环境
1. `PHP >= 5.4`

然而如果你的 `PHP` 版本小于 `7.1`，这段代码还是跑不了，会报`PHP Fatal error:  Cannot access empty property`，要将以下语句移除才能运行起来
```text
null           => '我是null',
$prop = null;
var_dump($dynamicVar->$prop);
```
我猜测应该是 `PHP 7.1` 加强了对 `nullable` `void` 的支持，所以导致了属性可以为 `null` 的诡异写法。

```php
<?php

class DynamicObj
{
    public function __construct($vars)
    {
        foreach ($vars as $var => $value) {
            $this->$var = $value;
        }
    }
}

$dynamicVar = new DynamicObj([
    null           => '我是null',
    0              => '我是数字',
    '1'            => '我也是数字',
    '0我是_- 非法属性名☺' => '。。。',
    0x123456       => 'hex test',
]);

var_dump($dynamicVar);

$prop = null;

var_dump($dynamicVar->$prop);

var_dump($dynamicVar->{'0我是_- 非法属性名☺'});

var_dump($dynamicVar->{0x123456});

$json = json_encode($dynamicVar);

var_dump($json);

var_dump(json_decode($json));
var_dump(json_decode($json, true));

```

```text
/Users/imac/Desktop/test.php:21:
class DynamicObj#1 (5) {
  public $ =>
  string(10) "我是null"
  public $0 =>
  string(12) "我是数字"
  public $1 =>
  string(15) "我也是数字"
  public $0我是_- 非法属性名☺ =>
  string(9) "。。。"
  public $1193046 =>
  string(8) "hex test"
}
/Users/imac/Desktop/test.php:25:
string(10) "我是null"
/Users/imac/Desktop/test.php:27:
string(9) "。。。"
/Users/imac/Desktop/test.php:29:
string(8) "hex test"
/Users/imac/Desktop/test.php:33:
string(188) "{"":"\u6211\u662fnull","0":"\u6211\u662f\u6570\u5b57","1":"\u6211\u4e5f\u662f\u6570\u5b57","0\u6211\u662f_- \u975e\u6cd5\u5c5e\u6027\u540d\u263a":"\u3002\u3002\u3002","1193046":"hex test"}"
/Users/imac/Desktop/test.php:35:
class stdClass#2 (5) {
  public $ =>
  string(10) "我是null"
  public $0 =>
  string(12) "我是数字"
  public $1 =>
  string(15) "我也是数字"
  public $0我是_- 非法属性名☺ =>
  string(9) "。。。"
  public $1193046 =>
  string(8) "hex test"
}
/Users/imac/Desktop/test.php:36:
array(5) {
  '' =>
  string(10) "我是null"
  [0] =>
  string(12) "我是数字"
  [1] =>
  string(15) "我也是数字"
  '0我是_- 非法属性名☺' =>
  string(9) "。。。"
  [1193046] =>
  string(8) "hex test"
}
```

突然觉得这么多年PHP白学了![EFDC0BB2E39E50386B1917CA74BA2CE4.jpg](https://storage.liesauer.net/2019/04/4010178035.jpg)