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PHP 类型提示与可见性

[英]PHP type hinting with visiblity

What is protected inside protected Service $service ? protected保护的protected Service $service中受保护的内容是什么?

public function __construct(protected Service $service)
 {
 }

What this feature is called?这个功能叫什么?

If i use protected then i do not need to declare and initialize the $service.如果我使用受保护,那么我不需要声明初始化$service。 how this is possible?这怎么可能?

class Sample
{
    public function __construct(protected Service $service)
    {
    }

    public function process()
    {
        $this->service->test();
    }
}

class Service
{

    public function test()
    {
        echo "test";
    }
}

$obj = new Sample(new Service());
$obj->process();

Its a short hand that introduced in PHP 8它是在 PHP 8 中引入的简写

Before: the definition of simple value objects requires a lot of boilerplate, because all properties need to be repeated at least four times.之前:简单值对象的定义需要大量的样板,因为所有的属性都需要至少重复四次。 Consider the following simple class:考虑以下简单的 class:

class Point {
    public float $x;
    public float $y;
    public float $z;
 
    public function __construct(
        float $x = 0.0,
        float $y = 0.0,
        float $z = 0.0,
    ) {
        $this->x = $x;
        $this->y = $y;
        $this->z = $z;
    }
}

After : But now as PHP introduced Constructor Property Promotion a short hand syntax, which allows combining the definition of properties and the constructor:之后:但是现在 PHP 引入了Constructor Property Promotion一种简写语法,它允许结合属性的定义和构造函数:

class Point {
    public function __construct(
        public float $x = 0.0,
        public float $y = 0.0,
        public float $z = 0.0,
    ) {}
}

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