Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:85977
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain lvl.fastmail.com designates 66.111.4.25 as permitted sender)
Message-ID: <1430169137.2886384.259330117.00E1734F@webmail.messagingengine.com>
To: internals@lists.php.net
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain
Date: Mon, 27 Apr 2015 23:12:17 +0200
Subject: Resolution of static variables in the function scope not using forwarded
 calling information?
From: php@lvl.fastmail.com

Hello all,

I ran into some very strange behavior while experimenting with static
function variables. It looks like a bug to me, but I couldn't find any
previous reports or discussions about the subject, so I wanted to gather
your input before submitting it as such.

Static variables in the function scope appear to be resolved using late
static binding: the content of the variable in that function is shared
amongst all instances of a class, though each subclass gets its own
separate variable space.

This is pretty logical and works fine. As an example, let's create
classes Base => Animal => {Cat,Dog}. Base has a function that describes
the class, and caches the result in a static function variable
$description. Calling describe() on the three different classes
correctly gives us three different results: http://3v4l.org/Qldve

However, once you override the describe function in Animal and call
parent::describe() from within, it looks like all calling information is
lost: the resolution of $description in Base's function scope now always
points to Animal's variable space. For example: http://3v4l.org/qWrvf

Overriding the function in one of the childmost classes like Dog gives
an even stranger result: $description is now correctly a separate value
in Cat vs Dog, but calling Animal::describe() now uses the value left by
its child class Cat?! See: http://3v4l.org/61P72

Any thoughts?

Thanks,
Laszlo