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To: internals@lists.php.net
Date: Wed, 7 Dec 2005 10:40:33 -0500
Subject: $this->this and avoiding circular references
From: apinstein@mac.com (Alan Pinstein)

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 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