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Date: Fri, 24 Nov 2023 13:34:14 +0100
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Subject: Re: [PHP-DEV] [RFC][Discussion] Why can constructors violate LSP?
From: php@dennis.birkholz.biz (Dennis Birkholz)

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Hi Robert,

Am 23.11.23 um 21:31 schrieb Robert Landers:
> However, we can make certain methods private anyway, namely,
> constructors (I haven't gone hunting for other built-in methods yet).
> This is perfectly allowed:
>
> class P {
>      public function __construct($name = 'waldo') {
>          echo "hello $name\n";
>      }
> }
>
> class C extends P {
>      private function __construct($name = 'world') {
>          parent::__construct($name);
>          echo "goodbye $name\n";
>      }
> }

you can enforce a public constructor by using an interface:

```
interface X {
     public function __construct (int $foo);
}

class A implements X {
     public function __construct (int $foo) {
         echo __CLASS__ . ": $foo\n";
     }
}

class B extends A {
     private function __construct (int $foo) {
         echo __CLASS__ . ": $foo\n";
     }
}
```

Which will give you the following error:
PHP Fatal error:  Access level to B::__construct() must be public (as in 
class X) in test.php on line 14

That way you put the definition of the constructor into the contract.

Greets
Dennis

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