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Date: Tue, 09 Dec 2014 11:18:33 +0000
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Subject: Re: [PHP-DEV] New function: spl_object_id() or spl_object_handle()
From: rowan.collins@gmail.com (Rowan Collins)

Nicolas Grekas wrote on 09/12/2014 09:31:
> Hi
>
>
> this is a proposal to add new function to PHP core: spl_object_id()
> IMHO this is a good idea: currently, var_dump has this super-power (and
> super-useful) capability of outputting a number that ease recognizing
> identical objects in dumps. This power should be transferred to userland
> devs so they can build their own tools.
>
> In fact, that's what I've done: since Symfony 2.6, you can dump using a
> userland function that (IMHO again) is more powerful than var_dump:
>
> http://symfony.com/doc/current/components/var_dumper/introduction.html
>
> In order to get an object's id, I use a trick that works for now:
> https://github.com/symfony/symfony/blob/2.6/src/Symfony/Component/VarDumper/Cloner/VarCloner.php#L258-L282

This seems like a very elaborate piece of reverse engineering for very 
little gain. If you just want to turn the result of spl_object_hash into 
a consistent integer, just use whatever re-hashing you like. The exact 
value of the "object handle" is not something you could ever do anything 
with anyway, surely?

> But I'd prefer replacing this trick by a dedicated function. So, with
> Julien Pauli, we worked on such a function. Symfony 2.6 also embeds a PHP
> extension that exposes more meta data about variables:
> https://github.com/symfony/symfony/tree/2.6/src/Symfony/Component/Debug/Resources/ext
>
> The function implemented in this extension is the root primitive that
> enables building a feature-full dumper, without resorting to tricks in PHP.

The more interesting part of this is the refcount - unlike 
spl_object_hash(), which does its job just fine, debug_zval_dump() *is* 
broken, because the documented use requires call-time pass-by-reference, 
which is actually impossible in current versions of PHP. A replacement 
would presumably need to hook in as a language construct rather than a 
function, so that the function call itself doesn't mess up the refcount 
and is_ref status of a ZVAL?

Regards,
-- 
Rowan Collins
[IMSoP]