PHP 8.1 中特定 class 的对象数组是否有类型提示？

Question

Is there a type hint in PHP 8.1 which allows using ExampleClass[] for declaring it is an array of objects of the class ExampleClass ?

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In my specific case, ExampleClass is called Task

What I want but does not work:

private Task[] $tasks;

My PHPStorm IDE tells me that Plural types are allowed only in doc types
- speaking that only in PHPDoc using Tasks[] would be totally fine. But I want to use plain PHP .

The error is: PHP Parse error: syntax error, unexpected token "[", expecting variable

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If I would only need one object Task and not an array of objects Task[] it would work with:

private Task $task;

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This is my current, working workaround:

private array $tasks;

Answer 1

The short answer is no.

My understanding is that enforcing such a thing has terrible performance problems. Some people want to go all the way and have full blown generics, others just want type-safe collections. Some people worry that implementing the latter first might hinder the development of the former in the future. So we're at a standstill.

There's the occasional discussion in the community such as this: https://externals.io/message/108175

Answer 2

While there is not a type hint available for such compound types, there is a workaround that enforces type. Create a subclass from ArrayObject and validate all values added to the ArrayObject. Then you can type hint your new subclass.

<?php

class Collection extends ArrayObject
{
    public function __construct(array $items = [])
    {
        foreach ($items as $item) {
            $this->validate($item)
        }
    }

    public function append($value): void
    {
        $this->validate($value);
        parent::append($value);
    }

    public function offsetSet($key, $value): void
    {
        $this->validate($value);
        parent::offsetSet($key, $value);
    }

    protected function validate($value): void
    {
        if (!$value instanceof Task) {
            throw new InvalidArgumentException(
                'Not an instance of Task'
            );
        }
    }
}

Now you can return objects with a type hint of Collection and it will behave exactly as an array of Task objects.