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Date: Fri, 09 Dec 2005 09:08:05 -0800
To: Jochem Maas <jochem@iamjochem.com>
Cc: Alan Pinstein <apinstein@mac.com>,internals@lists.php.net
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Subject: Re: [PHP-DEV] $this->this and avoiding circular references
From: andi@zend.com (Andi Gutmans)

Sorry about that. I think it might be a problem with the server not my client.
If it persists please let me know.

At 08:37 AM 12/9/2005, Jochem Maas wrote:
>Andi - your email client seems to be leaking :-)
>
>Andi Gutmans wrote:
>>Hi Alan,
>>Generally speaking, if you create a circular reference (whether by 
>>reference or by value), then you will have a "memory leak" until 
>>the end of the request. This is not only true for objects (and 
>>circular references might be indirect) but also for arrays.
>>This is a side-effect of reference counting systems, but within the 
>>way PHP is used within a request/response paradigm, it shouldn't be 
>>a real limiting factor in real-life usage. On the contrary, for 
>>these kind of apps, garbage collecting systems have potential to be 
>>significantly slower.
>>Andi
>>At 08:15 PM 12/7/2005, Alan Pinstein wrote:
>>
>>>My question is closely related to the one discussed on this php-dev
>>>thread:
>>>
>>>http://thread.gmane.org/gmane.comp.php.devel/32430
>>>
>>>Someone just sent me this link, which I didn't find myself when
>>>searching b/c the searches strip "this" from queries.
>>>
>>>Anyway, the question is related to reference counting of objects when
>>>assigned by value and by reference. It is a very important OO topic
>>>as the ability to have a non-ref-counted object "handle" is basically
>>>requisite to prevent circular reference deadlocks in OO projects.
>>>
>>>If the way I have proposed doesn't work, then what is the official
>>>way? And there *must* be one, otherwise, there is no way to avoid
>>>huge memory leaks (deferred release until end-of-script, I know, but
>>>it's a memory leak in the context of the script while it's running)
>>>with this kind of OO arrangement.
>>>
>>>In particular what confuses me is, why does, at least on PHP 5.0.4,
>>>this:
>>>
>>>$obj = &$this->this;    // doesn't seem to increment the refcount of the
>>>object
>>>
>>>behaves differently from:
>>>
>>>$obj = &$this;          // does seem to increment the refcount to the object
>>>
>>>References to $this should not only be valid, but are pretty much
>>>required for proper memory management in an OO environment, unless
>>>there is some other sanctioned way to get a weak reference... now I
>>>am not sure if the fact that making a & reference to an object
>>>doesn't increment the refcount is intended behavior, or an unintended
>>>side effect that may change. This is one of my major questions.
>>>
>>>Also, in regards to the thread linked above, I'd say that making & 
>>>$this an error is not desirable behavior; but maybe changing the
>>>value of $this should be (ie in C terms, $this is not an lvalue).
>>>Although, in C++/Obj-C you *can* even change this/self... in fact
>>>it's common in Obj-C:
>>>
>>>- (id) init
>>>{
>>>     if (self = [super init]) { /* etc */ }
>>>     return self;
>>>}
>>>
>>>Of course PHP is not Obj-C, but it's OO and garbage collected in a
>>>similar way, so PHP has the same need for manipulating $this; that
>>>is, creating weak references.
>>>
>>>Alan
>>>
>>>
>>>On Dec 7, 2005, at 11:27 AM, Antony Dovgal wrote:
>>>
>>>>On 07.12.2005 18:40, Alan Pinstein wrote:
>>>>
>>>>>Hi all-
>>>>
>>>><skip>
>>>>
>>>>Please use php-general@lists.php.net for questions regarding
>>>>development *in* PHP.
>>>>--
>>>>Wbr, Antony Dovgal
>>>
>>>
>>>--
>>>PHP Internals - PHP Runtime Development Mailing List
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