Type hinting for a child of a certain class

PHP
1

Is it possible to type hint for the child of a class? Say I only want to accept objects that were extended from the Products class, like Books.



class Product {}

class Book extends Product {}

class Cart
{
  public function __construct([Product Class Child] $product) // only accepts children of Product class
  {}

}

Something like that in the code above? It seems like it is possible, but I want to ensure I am not in error here.

2

Your example code is really confusing…
If I’m understanding this even remotely correctly, it sounds like you’d be better off with interfaces

3

Why don’t you type hint on the Product class itself? Any subclasses (child classes) of Product will be allowed through.

4

Returning to this post after a long time - it was a long week. Thanks for the responses.

Jeff:
Can you give me an example of a type hint on the product class? I am not used to type hinting yet and don’t know the ins and outs. From what you are suggesting, it looks like maybe if I type hint for class X, class X and all of its descendents will be accepted? Or am I wrong in this interpretation?

(So would this work?)


class Product
{
public function __construct(Product $product_class) {}
}
5

Arout:
I’m not sure how interfaces would help. I know some of the theory behind them, but putting it into practice is difficult for me. Could you give me a simple example of type hinting in an interface?

Would this work?


Interface MyInterface
{
public method doSomething(Product $product_class).
}

Would this require me to type hint for all doSomething methods in classes that implement this interface, or would it be done automatically so that I only need to make the method: “public method doSomething($product_class)” without the type hinting.