Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:63274
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: error (pb1.pair.com: domain mindplay.dk from 209.85.212.42 cause and error)
MIME-Version: 1.0
In-Reply-To: <CAL+t6cHwLMEsW+aRjGh7DZJ8h-6iK3wnHu9B-15RFj=DDYsG8w@mail.gmail.com>
References: <CADqTB_gemY8FubhTwH75LG4XB87MNMjScTpu2KUrqqagMXi38w@mail.gmail.com>
	<20121007200604.CGVT23973.aamtaout03-winn.ispmail.ntl.com@p2>
	<CADqTB_iYvbJ837BLPWXQzt0OJQWwAEa5V0rkTrbr=8Nn+Oy7ug@mail.gmail.com>
	<CAL+t6cHwLMEsW+aRjGh7DZJ8h-6iK3wnHu9B-15RFj=DDYsG8w@mail.gmail.com>
Date: Sun, 7 Oct 2012 22:00:27 -0400
Message-ID: <CADqTB_jnTzFcAXCho9p3mc1yQm1+8ZZ0v2DF8pDYhHFdA6nzpQ@mail.gmail.com>
To: internals@lists.php.net
Content-Type: text/plain; charset=ISO-8859-1
Subject: Re: [PHP-DEV] Re: Arrays which have properties of sets
From: rasmus@mindplay.dk (Rasmus Schultz)

looks like you're right - spl_object_hash() does in deed work... I
guess I was mislead by some of the notes people made in the
documentation... perhaps these should be moderated, and the
documentation should be update to clear up some of the mystery and
confusion that seems to surround this function?

http://us3.php.net/manual/en/function.spl-object-hash.php#110242

"Changing the state of an object does not affect the result" - well of
course not, since spl_object_hash() does not in fact seem to hash the
"object", or at least not it's state.

http://us3.php.net/manual/en/function.spl-object-hash.php#95666

"The unique identifiers of destroyed objects can and will be reused" -
this could be demonstrated more clearly by using unset() ... though I
understand it now, this example made me think at first that keys would
just be reused at random...

http://us3.php.net/manual/en/function.spl-object-hash.php#94647

"It seems that when switching scopes, the last one is repeated" -
that's not at all what's happening in this extremely misleading
example... rather, spl_object_hash(new stdClass()) creates an object
that immediately falls out of scope and gets destroyed, at which point
the same key may be reused in a different scope OR even in the same.

http://us3.php.net/manual/en/function.spl-object-hash.php#94060

this seems to demonstrate an alternative approach, but as pointed out
by Sherif, this is not the same thing at all.

http://us3.php.net/manual/en/function.spl-object-hash.php#91164

"The spl hash will always be the same for a given object, regardless
of content" - this is definitely not the case.

http://us3.php.net/manual/en/function.spl-object-hash.php#90296
http://us3.php.net/manual/en/function.spl-object-hash.php#87422

Both attempt to implement spl_object_hash() in older versions of PHP,
but both are extremely misleading since they have essentially nothing
in common with spl_object_hash() as such.

http://us3.php.net/manual/en/function.spl-object-hash.php#76220

This actually clarifies something things that probably should be
explained in the documentation.

It's perhaps the worst case of misleading user comments to date... ;-)


On Sun, Oct 7, 2012 at 7:51 PM, Sherif Ramadan <theanomaly.is@gmail.com> wrote:
> On Sun, Oct 7, 2012 at 7:12 PM, Rasmus Schultz <rasmus@mindplay.dk> wrote:
>> the manual states, "The implementation in SplObjectStorage returns the
>> same value as spl_object_hash()" - so I don't know how this would
>> really work any better than a custom implementation.
>>
>> perhaps safer would be to simply implement a collection-type that
>> requires the classes of elements in the collection to implement an
>> interface, exposing a unique key... and for objects that don't have a
>> unique key, generate sequential keys from a static counter in each
>> class... not ideal if you want to implement a document store that can
>> store "anything", since now every stored object/class needs to provide
>> a key...
>>
>
> How is that safer? If anything this introduces every aspect of being
> unsafe since relies on a user implementation that may or may not exist
> and may or may not be unique. As opposed to spl_object_hash, which can
> actually identify objects uniquely by looking at the internal symbol
> table that exposes all the objects in memory.
>
>> On Sun, Oct 7, 2012 at 4:06 PM, Jared Williams
>> <jared.williams1@ntlworld.com> wrote:
>>>
>>> See SPL's SplObjectStorage. That allows object instances as keys.
>>>
>>> Jared
>>
>> --
>> PHP Internals - PHP Runtime Development Mailing List
>> To unsubscribe, visit: http://www.php.net/unsub.php
>>