Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:108884
MIME-Version: 1.0
References: <CAF+90c9UZbpMM22YVywD9RGP_PBMv=AFDfMa8+BgJr=-f_he2Q@mail.gmail.com>
In-Reply-To: <CAF+90c9UZbpMM22YVywD9RGP_PBMv=AFDfMa8+BgJr=-f_he2Q@mail.gmail.com>
Date: Fri, 6 Mar 2020 10:29:42 +0100
Message-ID: <CAF+90c8q-xWpu0JPjH=AwsF_8zSnFSXxHpJXiuu=evbW_xRBcg@mail.gmail.com>
To: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="00000000000015490c05a02c4c8c"
Subject: Re: SimpleXMLIterator
From: nikita.ppv@gmail.com (Nikita Popov)

--00000000000015490c05a02c4c8c
Content-Type: text/plain; charset="UTF-8"

On Fri, Feb 28, 2020 at 11:59 AM Nikita Popov <nikita.ppv@gmail.com> wrote:

> Hi internals,
>
> I'm currently trying to make sure that all internal Traversable classes
> implement either Iterator or IteratorAggregate. This is a hard requirement
> for userland classes, but internal classes can get away with implementing
> only the internal get_iterator() mechanism. (
> https://github.com/php/php-src/pull/5216)
>
> One problem I ran into along the way is the SimpleXMLIterator class. A
> naive person might think that there is some sanity left in this world, and
> the hierarchy for SXE/SXI looks like this:
>
>     SimpleXMLElement implements IteratorAggregate
>     // where SimpleXMLElement::getIterator() returns:
>     SimpleXMLIterator implements Iterator
>
> Of course, they would be wrong. The actual hierarchy is this:
>
>     SimpleXMLElement implements Traversable
>     SimpleXMLIterator extends SimpleXMLElement implements Iterator
>
> The fact that SimpleXMLIterator extends SimpleXMLElement leaves me in a
> tough spot, because it means SimpleXMLElement cannot be an
> IteratorAggregate -- that would mean that SimpleXMLIterator implements both
> IteratorAggregate and Iterator, which is not permissible.
>
> It seems that it's also not possible to remove the "extends" without a
> non-trivial backwards-compatibility break, because apparently writing
> simplexml_load_string($str, 'SimpleXMLIterator') is a thing, which requires
> SimpleXMLIterator to extend SimpleXMLElement (and possibly is the reason
> why this was done in the first place.)
>
> The only way out I see here is to lift the methods from SimpleXMLIterator
> into SimpleXMLElement, make SimpleXMLElement implement Iterator itself, and
> basically leave SimpleXMLIterator as a dummy extension of SimpleXMLElement.
>
> Does that sound "reasonable"? Or rather, is there something more
> reasonable that can be done?
>

I've put up https://github.com/php/php-src/pull/5234 to implement this...

Nikita

--00000000000015490c05a02c4c8c--