Re: New function: spl_object_id() or spl_object_handle()

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]