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Subject: Re: [PHP-DEV] [RFC][VOTE] Objects as Keys
From: rowan.collins@gmail.com (Rowan Collins)

Stanislav Malyshev wrote on 17/12/2014 02:14:
> No, it's not possible. It is possible to call object method in an
> expression, and then use the result of the expression as an array key.
> But to do that you'd have to check that you're dealing with the object
> and the call the special method.

I think what Christoph was getting at is that you could implement an 
object map pretty simply by requiring the objects being added to 
implement a particular interface, as in:

...
function add ( Hashable $obj ) {
     $this->data[ $obj->getHash() ] = $obj;
}
...

The main thing that the current RFC would simplify is being able to 
accept a mixture of objects and scalars without performing an extra 
check; currently, you'd have to write something like this:

...
function add ( $scalar_or_obj ) {
     if ( is_scalar($scalar_or_obj) ) {
         $this->data[ $scalar_or_obj ] = $scalar_or_obj;
     } elseif ( $scalar_or_obj instanceOf Hashable ) {
         $this->data[ $obj->getHash() ] = $obj;
     } else {
         throw new InvalidArgumentException;
     }
}
...

Which is certainly uglier, any maybe was the case that Guilherme had in 
mind, but it's not like you have to build a whole new type of data 
structure, just add a few lines of implementation.

Compare that to trying to store the actual objects as keys, which would 
require a lot more than a few lines of code to emulate in pure PHP. 
Luckily, we have SplObjectStorage, which maybe makes that rather less 
urgent as well.

Regards,
-- 
Rowan Collins
[IMSoP]