Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:81515
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.220.43 as permitted sender)
Message-ID: <54CD8AEE.2070407@gmail.com>
Date: Sat, 31 Jan 2015 18:09:50 -0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.3.0
MIME-Version: 1.0
To: Andrea Faulds <ajf@ajf.me>
CC: Larry Garfield <larry@garfieldtech.com>, internals@lists.php.net
References: <CAEbg-4YrBumSmCmvTbgVQTS=U2dm3gLzO6im69qQp6brxm=RMg@mail.gmail.com> <54CBC804.7050706@gmail.com> <54CD7668.30301@garfieldtech.com> <54CD7975.8040908@gmail.com> <C524B7E9-86D2-42D1-AFA7-2A508A9A046D@ajf.me>
In-Reply-To: <C524B7E9-86D2-42D1-AFA7-2A508A9A046D@ajf.me>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Subject: Re: [PHP-DEV] [RFC] Immutable variables and objects
From: smalyshev@gmail.com (Stanislav Malyshev)

Hi!

> Here, there’s no redundant objects made, but if you pass $a on, it’d
> be automatically copied by PHP, so you don’t need to worry about it
> being modified.

I don't think it's a particularly good solution in this case, as in many
cases (especially DI setups, many design patterns, etc.) the whole point
of creating the object is to pass it around. Just pointlessly copying it
out of fear somebody somewhere could modify it doesn't sound the best
way. I'd rather just have a clear separation between mutating and
non-mutating APIs, and instruct people to use the right ones in right
situation - i.e. if you created the object or own it, use mutating ones,
if you got object from outside and do not have full ownership of it, use
non-mutating ones.

> Would that make sense? It’s no different than how our existing value
> types like scalars and arrays work.

Scalars don't have this problem as, except for string offsets (IMHO not
the best idea to have mutable strings too) scalars can not really be
changed, just replaced with other scalars. But implementing value
objects in PHP is not hard right now - if you don't provide any methods
that allow changing state, you've got an immutable object. It's just not
always what people using it would want, especially with something as
complex as HTTP message.
-- 
Stas Malyshev
smalyshev@gmail.com