PHP :: Request #70508 :: Support ::function similar to ::class

[2015-09-15 21:31 UTC] andreas at dqxtech dot net

Description:
------------
Classes like ReflectionFunction, ReflectionMethod, or built-in functions like array_filter() accept functions identified as strings.

This often leads to code like this, which is hard to analyse by the IDE:

$callback = '\MyVendor\MyLibraray\MyClass::foo';

For classes, I already use the ::class language construct to make this understandable to the IDE, and allow things like "Find usages", or to let the IDE tell me that the class does not exist.

I suggest to introduce a similar construct for functions and methods, ::function.

Test script:
---------------
class C {
  function fooMethod() {}
}

function fooFunction() {}

print C::fooMethod::function . "\n";
print fooFunction::function . "\n";

Expected result:
----------------
C::fooMethod
fooFunction


Actual result:
--------------
Fatal error: syntax error, unexpected T_DOUBLE_COLON

[2015-09-15 21:34 UTC] andreas at dqxtech dot net

So far my workaround is:

/* @see C::foo() */
$callback = 'C::foo';

This allows the IDE to "Find usages". But I need to manually check that the @see and the string are identical.

[2015-09-15 21:36 UTC] stas@php.net

-Package: PHP Language Specification +Package: Scripting Engine problem

[2015-09-15 21:50 UTC] requinix@php.net

See also https://wiki.php.net/rfc/function_referencing (withdrawn) which suggests
  $callback = &\MyVendor\MyLibrary\MyClass::foo;

There's the discussion for it too
  http://marc.info/?t=140710275400001&r=2&w=2
where "::function" also makes an appearance, but both solutions have problems.

[2015-09-15 22:29 UTC] andreas at dqxtech dot net

Well..

> See also https://wiki.php.net/rfc/function_referencing (withdrawn) which suggests
>  $callback = &\MyVendor\MyLibrary\MyClass::foo;

This is different in that it is meant to return a reference, whereas ::function would just return a string.

I am not convinced of the reference stuff, but I strings are nice and plain and simple.

> There's the discussion for it too
>   http://marc.info/?t=140710275400001&r=2&w=2
> where "::function" also makes an appearance, but both solutions have problems.

I read the issues some people raised for ::function, but I don't agree.
First, I don't know if the discussion meant ::function to return a reference or a string. I am very much advocating it to return a string, so it is consistent with ::class, and also has a simpler behavior.

The supposed ambiguity of AmIAFunctionOrAClass::function is not really a problem.

Right now, ::class does not trigger autoloading. Therefore, NonExistingClass::class will just return the class name, with no complaining.
Even existingFunction::class, for an existing function, will return "existingFunction" as if it was a class.

Likewise, ExistingClass::function should simply return "ExistingClass" as if it was a function. It should simply not care.

Otherwise, the mechanic behavior would depend on whether a class was already autoloaded or not. This would suck.

In fact ::class can already be abused as a funny alternative to string constants :)

[2015-12-19 04:23 UTC] ajf@php.net

The problem with functions is that in a namespace, if you do, say, `foo()`, PHP can't know whether that's `\foo()` or `\someNamespace\foo()` without running the autoloader.

[2015-12-19 04:23 UTC] ajf@php.net

Or, well, PHP does not have an autoloader for functions just now. But if it did, this would be a problem. And either way we can't do it at compile-time.

[2016-03-26 21:46 UTC] krakjoe@php.net

-Status: Open +Status: Suspended

[2016-03-26 21:46 UTC] krakjoe@php.net

For this kind of change, an RFC is required.

Please see: https://wiki.php.net/rfc/howto

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