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Date: Wed, 7 Dec 2005 21:27:52 -0500
To: internals@lists.php.net
Subject: Re: [PHP-DEV] $this->this and avoiding circular references
From: apinstein@mac.com (Alan Pinstein)

> are you using ph4 or php5?

PHP5

> are you setting $this->this yourself or 'is it just there'?

No, I'm not setting it, just reading it (see addChildObject() code  
below), if that's what you mean.

-Alan

>
> 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
>