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Date: Wed, 13 Dec 2017 00:01:57 -0500
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To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Cc: Stanislav Malyshev <smalyshev@gmail.com>, Nikita Popov <nikita.ppv@gmail.com>, 
	PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Explicit call-site send-by-ref syntax
From: pollita@php.net (Sara Golemon)

On Tue, Dec 12, 2017 at 2:43 AM, Johannes Schl=C3=BCter
<johannes@schlueters.de> wrote:
> The issue, as you well know, is that references disable copy-on-write. Th=
us assume you have code like this:
>
> function with_ref(&$a) {
>    count ($a);
> }
>
> function no_ref($a) {
>   count($a);
> }
>
> The count in with_ref() will copy the array, while no_ref() can use copy =
on write and won't actually copy.
>
That *was* true in PHP 5.

In PHP 7, the with_ref() version has a very slight overhead boxing the
array into an IS_REF zval, then unboxing it for the call to count().
This isn't a deep (or even shallow) copy. It's one extra zval alloc
and a few integer ops.

-Sara