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Date: Tue, 24 Oct 2023 14:57:55 +0200
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To: Jordan LeDoux <jordan.ledoux@gmail.com>
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Subject: Re: [PHP-DEV] Custom object equality
From: dik.takken@gmail.com (Dik Takken)

On 23-10-2023 22:07, Jordan LeDoux wrote:
> I don't quite follow. The interface would cause the engine to use the
> result of an `equals()` function on the object if it implements an
> interface as part of `zend_compare`? Internally there is no `==` function,
> there is only the equivalent of `<=>`. To implement it ONLY for `==` would
> require a trapdoor of some kind in the `do_operation` handler that would
> also affect the way the existing extensions work, such as the `DateTime`
> class which implements a custom handler for the `compare` handler on the
> zend class entry.

No, the interface would not cause anything to happen in `zend_compare`. 
It would simply serve to make explicit that an object has a custom 
implementation of a (set of) operators and that the implementing method 
can be called directly. So the developer can choose to either use the 
operator or call the implementing method on the object. Both styles 
would be supported and the following two expressions would be equivalent:

   $a == $b
   $a->equals($b)

(the method name is just an example)

Regarding your (Jordan's) RFC on the subject: The method call style 
would not yield readable code in this case, as the 'methods' are named 
after the operators. So that part of the RFC would need to change to 
make both styles work.

Regards,
Dik