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
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/QldveHowever, 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/qWrvfOverriding 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
This last is the only one that seems to be a bug to me; I think if you
step through the others you'll see why they are fine. Maybe the last
isn't a bug either; I'll try to think about this more but it does
appear to be a bug.
Any thoughts?
Thanks,
Laszlo
This last is the only one that seems to be a bug to me; I think if you
step through the others you'll see why they are fine. Maybe the last
isn't a bug either; I'll try to think about this more but it does
appear to be a bug.
FWIW, an example that makes the second situation slightly more clear:
http://3v4l.org/CcrL8
I would have expected the static function variable and
get_called_class() to always refer to the same class/variable space,
parent:: or not.
Oddly enough, referring to static class variables with "static::" never
seems to use late static binding at all? http://3v4l.org/G9nCE
Thanks,
Laszlo