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Date: Wed, 07 Dec 2005 17:12:11 +0100
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To: Alan Pinstein <apinstein@mac.com>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] $this->this and avoiding circular references
From: jochem@iamjochem.com (Jochem Maas)

are you using ph4 or php5?
are you setting $this->this yourself or 'is it just there'?

Alan Pinstein wrote:
> Hi all-
> 
> I've been trying to avoid circular references in some data import  
> scripts and finally figured out how to do it. However, I wanted to  ask 
> you guys to make sure that what I'm doing is something that's  legit and 
> can be relied on into the future.
> 
> Also, please note that I tried searching the archives for "this" and  
> "this->this" but the searcher keeps removing "this" from my query! So  
> sorry if this is asked and answered....
> 
> So, my objects are in a parent-child relationship and they both have  
> links to each other... pretty standard circular reference scenario:
> 
> 
>> ParentObject:
>>
>> function addChildObject($c)
>> {
>>     $this->children[] = $c;
>>     $c->setParent($this->this);        // this syntax is the only way 

assuming php4, I would say this these lines should be (difficult
to tell though, without more insight/code/brains to play with ;-):

function addChildObject(&$c) {
        $this->children[] =& $c;
        $c->setParent( $this );
}

>> I  found to make "$this" not get refcounted here
>> }
>>
>> Now, to make this work as it should without incrementing the ref  
>> counts when storing the link to the parent, setParent() needs to  have 
>> a non-refcounted pointer to the object:
>>
>> ChildObject:
>>
>> // need & in both places to make the ref not get ref-counted
>> function setParent(&$parent)
>> {
>>    $this->-parent = &$parent;
>> }
> 
> 
> My question is, is "$this->this" valid syntax? Can it be relied on?  Is 
> my overall approach sane?
> 
> It's very important that I get memory management working in such a  way 
> here because the objects are used in large loops for importing  data, 
> and without this, the script uses unbounded amounts of memory.  With 
> this, it uses a finite amount of memory and works beautifully.
> 
> Thanks in advance,
> Alan
>