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Date: Thu, 15 Sep 2005 14:15:02 +0300
To: "Ron Korving" <r.korving@xit.nl>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] references in arrays
From: zeev@zend.com (Zeev Suraski)
References: <81.1E.41173.93F49234@pb1.pair.com>

At 13:35 15/09/2005, Ron Korving wrote:
>Hi,
>
>For performance' sake, I have to know if this is true:
>
>Is it the case that when I do this:
>
><?php
>   $array = array("one" => array(0,1,2), "two" => array(4,5,6));
>   $one = $array["one"];
>?>
>
>That $one is not a copy, but a reference to $array["one"] and will only
>become a copy when I alter the contents of $one?

That's correct.

>I know this is the case for
>regular variables, but does this also go for contents of arrays? If not, I
>need to use the ampersand like I used to. But if it really is just a
>reference, that would be good to know as I shouldn't be using the ampersand
>at all (mistakingly thinking it's a performance advantage when it's actually
>not).

Generally, using & where it's not necessary is more often than not a 
performance disadvantage, and not an advantage.  You should never use & for 
better performance, only if you need it for applicative usage.  The engine 
would do its best to do the least copying on its own.

Zeev