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Date: Wed, 10 Mar 2004 16:30:29 +0100 (CET)
To: Robert Cummings <robert@interjinn.com>
cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] Question about internal workings of references/variables.
From: derick@php.net (Derick Rethans)

On Wed, 10 Mar 2004, Robert Cummings wrote:

> Hi Internals,
>
> I'd like to confirm/refute some knowledge I think I have of the PHP
> internal workings with respect to variables and references. I believe
> that when a variable is assigned the value of another variable an
> internal reference is created and some bit is used to keep track of
> whether the value should be copied when an attempt is made to change
> either the original variable or the newly assigned variable (maybe this
> isn't the case for integers or floats since the performance would be
> similar). Can anyone confirm or elaborate further?

yes, that is true and called "copy-on-write". It's done for all types of
variables though.

> Also I think I remember hearing once upon a time that creating a
> reference in PHP script is more work than creating a copy when the copy
> won't be altered? Can this be confirmed also?

Never tried that myself, but I believe it to be true.
>
> Last but not least, do objects work under the same principles?

yes, in php 4 they do. in php 5 it is true for "object-handles" and not
objects, but that shouldn't be of any concern.

regards,
Derick