从未停止前进，PHP8.1带来了8个重要的新转变！

1、枚举（Enums）

enum Status
{
    case draft;
    case published;
    case archived;
    
    public function color(): string
    {
        return match($this) 
        {
            Status::draft => 'grey',   
            Status::published => 'green',   
            Status::archived => 'red',   
        };
    }
}

2、只读属性（Readonly properties）

class PostData
{
    public function __construct(
        public readonly string $title,
        public readonly string $author,
        public readonly string $body,
        public readonly DateTimeImmutable $createdAt,
        public readonly PostState $state,
    ) {}
}

3、初始化程序中的新内容（New in initializers）

class PostStateMachine
{
    public function __construct(
        private State $state = new Draft(),
    ) {
    }
}

4、纤维，又名“绿线”（Fibers, a.k.a. "green threads"）

$fiber = new Fiber(function (): void {
    $valueAfterResuming = Fiber::suspend('after suspending');
    
    // … 
});
 
$valueAfterSuspending = $fiber->start();
 
$fiber->resume('after resuming');

5、数组解包也支持字符串键（Array unpacking also supports string keys）

$array1 = ["a" => 1];
$array2 = ["b" => 2];
$array = ["a" => 0, ...$array1, ...$array2];
var_dump($array); // ["a" => 1, "b" => 2]

6、一种可调用类（First class callables）

function foo(int $a, int $b) { /* … */ }
$foo = foo(...);
$foo(a: 1, b: 2);

7、纯交集类型（Pure intersection types）

function generateSlug(HasTitle&HasId $post) {
    return strtolower($post->getTitle()) . $post->getId();
}

8、新array_is_list功能（The new array_is_list function）

$list = ["a", "b", "c"];
array_is_list($list); // true
$notAList = [1 => "a", 2 => "b", 3 => "c"];
array_is_list($notAList); // false
$alsoNotAList = ["a" => "a", "b" => "b", "c" => "c"];
array_is_list($alsoNotAList); // false

本文系翻译，原文地址：https://stitcher.io/blog/php-81-in-8-code-blocks