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Date: Sun, 2 Aug 2015 19:41:48 +0200
CC: Anatol Belski <anatol.php@belski.net>,
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To: Stanislav Malyshev <smalyshev@gmail.com>
Subject: Re: [PHP-DEV] Exposing object handles to userland
From: bobwei9@hotmail.com (Bob Weinand)

As I describe below, I agree with Nikita on spl_object_id().

> Am 02.08.2015 um 08:52 schrieb Stanislav Malyshev =
<smalyshev@gmail.com>:
>=20
> Hi!
>=20
> Some suspicious use of spl_object_hash() out there...
>=20
>> =
https://github.com/symfony/symfony/blob/master/src/Symfony/Component/VarDu=
mper/Cloner/VarCloner.php
>=20
> Not sure what this one does... but calculations with spl_object_hash()
> look very suspicious.

Actually, it's doing the right thing=E2=80=A6 calculating the value the =
object id is xor'ed with (as we know that consecutively defined objects =
have consecutive ids).
It's relying on the implementation of spl_object_hash() and will even =
continue to work when we remove that part of randomness as that value =
it's xor'ed with is then nothing else than 0.

That's why we should expose spl_object_id()=E2=80=A6 so that such hacks =
are unnecessary.

>> =
https://github.com/horde/horde/blob/master/imp/lib/Factory/MimeViewer.php
>=20
> This one _might_ be doing it right, but not sure as basing caching
> instances on hash of a (mutable) object may produce weird results.

It works and I'm using it that way too=E2=80=A6 that's currently what =
spl_object_hash is good for. The only issue is when it overflows after =
2^32 objects. Though it isn't an issue on 64 bit systems=E2=80=A6

>> =
https://github.com/horde/horde/blob/master/framework/Support/lib/Horde/Sup=
port/Randomid.php
>=20
> Oh wow, what's going on there? That's obviously not a proper use of
> spl_object_hash().

Yup, that one is misuse as source of entropy=E2=80=A6 while it doesn't =
really provide much more entropy as it's internally anyway xor'ed with =
mt_rand().

>> =
https://github.com/WordPress/WordPress/blob/master/wp-includes/plugin.php
>=20
> I guess this one is wrong too, as it mentions storage, and storing
> object ID is pointless. Maybe I am misunderstanding what "storage" =
means
> there.

The storage is only used in case spl_object_hash() does not exist for =
trying to get an unique identifier for that object (Wordpress has 5.2 =
compatibility, yeah=E2=80=A6).

The object id / hash is basically just an identifier for an object in =
PHP, just like we sometimes put pointers in e.g. a binary tree to easily =
map two pointers together in C.

> --=20
> Stas Malyshev
> smalyshev@gmail.com

Bob=