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Subject: Re: [PHP-DEV] Inconsistencies in callable, call_user_func and direct
 variable calls
From: rowan.collins@gmail.com (Rowan Collins)

Sebastian B.-Hagensen wrote on 19/03/2015 16:27:
> Another way to unify array and string callback may be to use the
> callable syntax and have it return a closure:
> callable('strlen');
> callable($object, $methodName);
> callable('class', 'staticMethod')

Andrea proposed a slightly different syntax for function references a 
few months back - see withdrawn RFC [1] and accompanying Internals 
thread [2].

I actually quite like the callable() syntax. Whereas Andrea's suggestion 
was a parser rule that took a bare string, like &foo, this would have to 
always take a string, like callable('foo'), but that's good if we want 
to roll in dynamic callbacks as well:

Right now, we have to embed the type information in the variable name, 
because this is just a string:
$hook_callback = 'hook_' . $hook_name;
This has a much strong information scent:
$hook = callable('hook_' . $hook_name);

There's then the question of what kind of object it would return - a 
Closure? Some child or sibling of Closure? What methods could be 
usefully provided?

What should happen if the arguments provided aren't callable? Throw an 
exception?

Also, do we still need a way to delay testing of callability, to allow this:

class A {
     private function foo() { echo 'foo'; }
     public function bar(callable $call) { $call(); }
}
$a = new A;
// A::foo is not callable here, but will be when we get inside A::bar
var_dump(is_callable([$a, 'foo'] ));
$a->bar( [$a, 'foo'] );

Currently works: http://3v4l.org/pNZgn


[1] https://wiki.php.net/rfc/function_referencing
[2] http://marc.info/?t=140710275400001&r=2&w=2

Regards,
-- 
Rowan Collins
[IMSoP]